Revert creation of repostiory_read_only column in namespaces tables

What does this MR do?

This MR undoes !51800 (merged) because it was impossible to get the lock in production to create the column in that table.

Incident issue gitlab-com/gl-infra/production#3390 (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

Refs #299052 (closed)