Fix suggestion dropdown blocking buttons after mention

What does this MR do?

Adds a return after entering a comment so as to close the suggestion dropdown if it exists.

Closes #225346 (closed)

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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