Rename internal file used to deny pushes for certain files

What does this MR do?

Renames file to ee/lib/gitlab/checks/files_denylist.yml

Related issue: #219990 (closed)

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.