Explicitly import gl_dropdown

What does this MR do?

Adds missing ~/gl_dropdown imports

Replaces gitlab-foss!32832 (closed)

See #31702 (closed) for details

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