Rename helper file to be consistent with its module name

What does this MR do and why?

• Renaming the helper file name to be consistent with its module name
• i.e. the module name is PackagesManagerApiSpecHelpers but the file name is packages_manager_api_spec_helper.rb
• This should be consistent in order to support tooling, etc.
• Note: I noticed this inconsistency when working on the refactoring as part of Draft: refactor: Better shared examples for pyp... (!135552)

The helper is used in the following files:

• ee/spec/requests/api/pypi_packages_spec.rb
• spec/requests/api/go_proxy_spec.rb
• spec/requests/api/ml_model_packages_spec.rb
• spec/requests/api/pypi_packages_spec.rb
• spec/requests/api/rubygem_packages_spec.rb
• spec/requests/api/terraform/modules/v1/packages_spec.rb
• spec/services/packages/composer/create_package_service_spec.rb
• spec/services/packages/nuget/check_duplicates_service_spec.rb
• spec/services/packages/pypi/create_package_service_spec.rb

🛠 with ❤ at Siemens

Screenshots or screen recordings

Only backend. There are no changes in the frontend .

How to set up and validate locally

1. Run the tests files that us this helper

bundle rspec ee/spec/requests/api/pypi_packages_spec.rb spec/requests/api/go_proxy_spec.rb spec/requests/api/ml_model_packages_spec.rb spec/requests/api/pypi_packages_spec.rb spec/requests/api/rubygem_packages_spec.rb spec/requests/api/terraform/modules/v1/packages_spec.rb spec/services/packages/composer/create_package_service_spec.rb spec/services/packages/nuget/check_duplicates_service_spec.rb spec/services/packages/pypi/create_package_service_spec.rb 

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.
  • Changelog entry added, if necessary
  • Documentation created/updated via this MR
  • Documentation reviewed by technical writer or follow-up review issue created
  • Tests added for this feature/bug
  • Tested in all supported browsers
  • Conforms to the code review guidelines
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