[DOCS] Fix headings for Azure, GCS, and S3 snapshot repo pages

docs/reference/snapshot-restore/repository-azure.asciidoc

@@ -1,11 +1,11 @@
 [[repository-azure]]
-=== Azure Repository
+=== Azure repository
 
 You can use https://docs.microsoft.com/en-us/azure/storage/blobs/storage-blobs-introduction[Azure Blob storage] as a repository for
 {ref}/modules-snapshots.html[Snapshot/Restore].
 
 [[repository-azure-usage]]
-==== Azure Repository
+==== Setup
 
 To enable Azure repositories, you have first to define your azure storage settings as
 {ref}/secure-settings.html[secure settings], before starting up the node:

docs/reference/snapshot-restore/repository-gcs.asciidoc

@@ -1,5 +1,5 @@
 [[repository-gcs]]
-=== Google Cloud Storage Repository
+=== Google Cloud Storage repository
 
 You can use the https://cloud.google.com/storage/[Google Cloud Storage]
 service as a repository for {ref}/modules-snapshots.html[Snapshot/Restore].
@@ -15,7 +15,7 @@ and create a new project. After your project is created, you must enable the
 Cloud Storage Service for your project.
 
 [[repository-gcs-creating-bucket]]
-===== Creating a Bucket
+===== Creating a bucket
 
 The Google Cloud Storage service uses the concept of a
 https://cloud.google.com/storage/docs/key-terms[bucket] as a container for all
@@ -38,7 +38,7 @@ For more detailed instructions, see the
 https://cloud.google.com/storage/docs/quickstart-console#create_a_bucket[Google Cloud documentation].
 
 [[repository-gcs-service-authentication]]
-===== Service Authentication
+===== Service authentication
 
 The repository must authenticate the requests it makes to the Google Cloud Storage
 service. It is common for Google client libraries to employ a strategy named https://cloud.google.com/docs/authentication/production#providing_credentials_to_your_application[application default credentials].
@@ -54,7 +54,7 @@ credentials if you are using an environment that does not support automatic
 credential discovery.
 
 [[repository-gcs-using-service-account]]
-===== Using a Service Account
+===== Using a service account
 You have to obtain and provide https://cloud.google.com/iam/docs/overview#service_account[service account credentials]
 manually.
 
@@ -125,7 +125,7 @@ of the client's `credentials_file` settings. They complete using the client as
 it was built when the operation started.
 
 [[repository-gcs-client]]
-==== Client Settings
+==== Client settings
 
 The client used to connect to Google Cloud Storage has a number of settings available.
 Client setting names are of the form `gcs.client.CLIENT_NAME.SETTING_NAME` and are specified
@@ -191,18 +191,8 @@ are marked as `Secure`.
     can be specified explicitly. For example, it can be used to switch between projects when the
     same credentials are usable for both the production and the development projects.
 
-`proxy.host`::
-    The host name of a proxy to connect to the Google Cloud Storage through.
-
-`proxy.port`::
-    The port of a proxy to connect to the Google Cloud Storage through.
-
-`proxy.type`::
-    The proxy type for the client. Supported values are `direct`, `http`, and `socks`.
-    The default value is `direct` (no proxy).
-
 [[repository-gcs-repository]]
-==== Repository Settings
+==== Repository settings
 
 The `gcs` repository type supports a number of settings to customize how data
 is stored in Google Cloud Storage.
@@ -262,7 +252,7 @@ include::repository-shared-settings.asciidoc[]
     Name used by the client when it uses the Google Cloud Storage service.
 
 [[repository-gcs-bucket-permission]]
-===== Recommended Bucket Permission
+===== Recommended bucket permission
 
 The service account used to access the bucket must have the "Writer" access to the bucket:
 

docs/reference/snapshot-restore/repository-s3.asciidoc

@@ -1,13 +1,13 @@
 [[repository-s3]]
-=== S3 Repository
+=== S3 repository
 
 You can use AWS S3 as a repository for {ref}/modules-snapshots.html[Snapshot/Restore].
 
 *If you are looking for a hosted solution of Elasticsearch on AWS, please visit
 https://www.elastic.co/cloud/.*
 
 [[repository-s3-usage]]
-==== Getting Started
+==== Getting started
 
 To register an S3 repository, specify the type as `s3` when creating
 the repository. The repository defaults to using
@@ -30,7 +30,7 @@ PUT _snapshot/my_s3_repository
 
 
 [[repository-s3-client]]
-==== Client Settings
+==== Client settings
 
 The client that you use to connect to S3 has a number of settings available.
 The settings have the form `s3.client.CLIENT_NAME.SETTING_NAME`. By default,
@@ -233,7 +233,7 @@ use as a snapshot repository. You will need to work with the supplier of your
 storage system to address any incompatibilities you encounter.
 
 [[repository-s3-repository]]
-==== Repository Settings
+==== Repository settings
 
 The `s3` repository type supports a number of settings to customize how data is
 stored in S3. These can be specified when creating the repository. For example:
@@ -359,7 +359,7 @@ This sets up a repository that uses all client settings from the client
 `my.s3.endpoint` by the repository settings.
 
 [[repository-s3-permissions]]
-===== Recommended S3 Permissions
+===== Recommended S3 permissions
 
 In order to restrict the Elasticsearch snapshot process to the minimum required
 resources, we recommend using Amazon IAM in conjunction with pre-existing S3
@@ -480,7 +480,7 @@ reach a certain age.
 
 [[repository-s3-aws-vpc]]
 [discrete]
-==== AWS VPC Bandwidth Settings
+==== AWS VPC bandwidth settings
 
 AWS instances resolve S3 endpoints to a public IP. If the Elasticsearch
 instances reside in a private subnet in an AWS VPC then all traffic to S3 will