Fix incorrect trigger of issue/epic autocomplete

What does this MR do and why?

Fixes a bug Related Items app where;

• Issues autocomplete would trigger on typing # within Add an existing epic form.
• Epics autocomplete would trigger on typing & within Add an existing issue form.

Screenshots or screen recordings

Screen_Recording_2021-09-27_at_5.16.55_PM

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #339596 (closed)