If completions menu is already displayed, don't select inline completion (#22977)

Before this change, inline completion would displace the user's
selection. Unfortunately this brings less visibility to the inline
completion, I think a good solution to this will be to display a chunk
of the completion inline in the menu, and have a WIP change for that.
Since the current behavior is frustrating, not blocking this improvement
on that

Release Notes:

- N/A