Remove custom Danger check for frozen_string_literal comments

What does this MR do?

This is redundant with Rubocop's Style/FrozenStringLiteralComment cop, which we didn't have enabled when this was introduced.

To preserve the same behaviour we also:

• Switch to EnforcedStyle: always_true, to forbid false values.
• Replace the wildcard list with an explicit list of all violations, so we still catch all newly added files.

The violations will be fixed in follow-up MRs: #299105 (closed)

Verified that CI was still failing with a temporary commit: https://gitlab.com/gitlab-org/gitlab/-/jobs/970390238

For reference, the Danger check was introduced in gitlab-foss!20767 (merged), the cop was enabled in gitlab-foss!21999 (merged), and default-enabled in gitlab-styles in https://gitlab.com/gitlab-org/gitlab-styles/-/merge_requests/37.

This change was prompted by !51486 (merged)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] 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