Remove .gitlab folder under package gitlab-rails

What does this MR do and why?

This is a backport of !9215 (merged)

SLES 12 sp 5 is running rpm 4.11.2 .

This version has a max limit of 16 mebibytes that it accepts in the header data of an installed rpm in the rpm database.

We're close to breaching this limit on this distro. Often we find ourselves just a few hundreds of bytes above the limit.

In this MR I am removing:

• Under embedded/service/gitlab-rails
• .gitlab folder You can see its contents here - 179 files

Under embedded/lib/ruby/gems:

• .gitlab-ci.yml files - 16 files
• .gitignore - 198 files
• .travis.yml - 65 files
• .rubocop*.yml - 97 files
• .rspec - 97 files
• .github folders - 221 files

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The original MR has been deployed to GitLab.com (not applicable for documentation or spec changes).
• This MR has a severity label assigned (if applicable).

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).