Improve emoji autocomplete when typing :) or :(

What does this MR do and why?

This prevents confusion due to matching of emoji descriptions when a single parenthesis is entered.

This "bug" surfaced once we fixed a different bug in https://gitlab.com/gitlab-org/gitlab/-/issues/343358

Screenshots or screen recordings

Screen_Recording_2021-11-11_at_9.20.57_AM

How to set up and validate locally

1. Type :) or :( in Markdown input fields.

MR acceptance checklist

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