Fix Rust 1.83.0 "elided_named_lifetimes" warning. (#3955)

Compiling aws-config v1.5.12 (.../aws-config)
warning: elided lifetime has a name
   --> .../aws-config/src/meta/credentials/chain.rs:117:72
    |
117 | fn provide_credentials<'a>(&'a self) ->
future::ProvideCredentials<'_>
| -- lifetime `'a` declared here ^^ this elided lifetime gets resolved
as `'a`
    |
    = note: `#[warn(elided_named_lifetimes)]` on by default

warning: elided lifetime has a name
   --> .../aws-config/src/meta/token.rs:108:60
    |
108 |     fn provide_token<'a>(&'a self) -> future::ProvideToken<'_>
| -- lifetime `'a` declared here ^^ this elided lifetime gets resolved
as `'a`

warning: elided lifetime has a name
   --> .../aws-config/src/sts/assume_role.rs:317:72
    |
317 | fn provide_credentials<'a>(&'a self) ->
future::ProvideCredentials<'_>
| -- lifetime `'a` declared here ^^ this elided lifetime gets resolved
as `'a`

## Motivation and Context
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## Description
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## Testing
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- [ ] For changes to the smithy-rs codegen or runtime crates, I have
created a changelog entry Markdown file in the `.changelog` directory,
specifying "client," "server," or both in the `applies_to` key.
- [ ] For changes to the AWS SDK, generated SDK code, or SDK runtime
crates, I have created a changelog entry Markdown file in the
`.changelog` directory, specifying "aws-sdk-rust" in the `applies_to`
key.

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._

---------

Co-authored-by: Landon James <[email protected]>

aws/rust-runtime/aws-config/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aws-config"
-version = "1.5.12"
+version = "1.5.13"
 authors = [
     "AWS Rust SDK Team <[email protected]>",
     "Russell Cohen <[email protected]>",

aws/rust-runtime/aws-config/src/meta/credentials/chain.rs

@@ -114,7 +114,7 @@ impl CredentialsProviderChain {
 }
 
 impl ProvideCredentials for CredentialsProviderChain {
-    fn provide_credentials<'a>(&'a self) -> future::ProvideCredentials<'_>
+    fn provide_credentials<'a>(&'a self) -> future::ProvideCredentials<'a>
     where
         Self: 'a,
     {

aws/rust-runtime/aws-config/src/meta/token.rs

@@ -105,7 +105,7 @@ impl TokenProviderChain {
 }
 
 impl ProvideToken for TokenProviderChain {
-    fn provide_token<'a>(&'a self) -> future::ProvideToken<'_>
+    fn provide_token<'a>(&'a self) -> future::ProvideToken<'a>
     where
         Self: 'a,
     {

aws/rust-runtime/aws-config/src/sts/assume_role.rs

@@ -314,7 +314,7 @@ impl Inner {
 }
 
 impl ProvideCredentials for AssumeRoleProvider {
-    fn provide_credentials<'a>(&'a self) -> future::ProvideCredentials<'_>
+    fn provide_credentials<'a>(&'a self) -> future::ProvideCredentials<'a>
     where
         Self: 'a,
     {