Include merge method link in attribute description

What does this MR do?

Currently, the project visibility methods attribute description link to the descriptions and options for visibility methods. The merge methods attribute description doesn't, but it should do the same.

Closes: #64282 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content