Centralize Ruby Version to .ruby-version

The `.ruby-version` file is the ecosystem standard for defining a Ruby version.  This PR adds the `.ruby-version` file, ensures a `required_ruby_version` is set, and removes all other references to Ruby in this repository, aligning it with the standard.
> [!IMPORTANT]
> Please verify the following before merging:

Verify that the changes in the PR meets the following requirements or adjust manually to make it compliant:
  - [ ] `.ruby-version` file is present with the correct Ruby version defined
  - [ ] A `required_ruby_version` in your gemspec is set
  - [ ] There is no Ruby version present in the  `dev.yml` Ruby task (before: `- ruby: x.x.x`, after: `- ruby`)
  - [ ] There is no Ruby version/requirement referenced in the `Gemfile` (no lines with `ruby  <some-version>`)
  - [ ] A `Gemfile.lock` is built with the defined Ruby version
  - [ ] The version of Rubocop installed is 1.61.0 or greater
  - [ ] There is no `TargetRubyVersion` defined  in `rubocop.yml`
  - [ ] There is no Ruby argument  present in  `ruby/setup-ruby` Github Actions that do **not**  run on a Ruby matrix (no lines with `ruby-version: “x.x”`)

This PR will be merged if there isn't any activity after 4 weeks.

.rubocop.yml

@@ -2,7 +2,6 @@ inherit_gem:
   rubocop-shopify: rubocop.yml
 
 AllCops:
-  TargetRubyVersion: 2.7
   Exclude:
     - 'vendor/**/*'
     - 'gemfiles/vendor/**/*'

.ruby-version

@@ -0,0 +1 @@
+3.2.2

dev.yml

@@ -1,7 +1,7 @@
 name: erb-lint
 
 up:
-  - ruby: '3.2.2'
+  - ruby
   - bundler
 
 commands: