Hides Close MR button on merged MR

What does this MR do?

When a Merge request is merged, shows only the Report abuse menu item in the dropdown menu instead of showing the close_reopen_report toggle with and unusable Close button.

The Report abuse is still hidden when the author of the Merge request is the current_user.

As discussed here this MR also hides the Reopen button on a closed and locked issue when the issue.author is not the current_user

Screenshot

before:

after:

What are the relevant issue numbers?

#50161 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #50161 (closed)