Upgrade gitlab-styles to version 6.2.0

What does this MR do?

This MR upgrades to gitlab-styles 6.2.0.

New check rules

This upgrade enables the following cops:

• Performance/OpenStruct - 16 offenses
  • Make sure this static analysis check rule is enabled for new usage
  • Current offenses are ignored but will be fixed as a separate iteration: #325744 (closed)
• RSpec/EmptyLineAfterFinalLet - 1162 offenses
  • Make sure this static analysis check rule is enabled for new usage
  • Current offenses are ignored but will be fixed as a separate iteration: TODO

• Once approved and merged by a maintainer, mention new rules again:
  • In the relevant Slack channels (e.g. #development, #backend, #frontend)
  • (Optional depending on the impact of the change) In the Engineering Week in Review

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • [-] I have included a changelog entry.
  • I have not included a changelog entry because it's not a user-facing change.
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team