Mentions do not work in "Text" mode on comments.

Description

Mention do no work in Text mode.

How to reproduce

1. Create any issue(Xray or Jira).
2. Click on the issue.
3. Disable browser-side cache.

1. Reload the page with comments in "Text" mode.
2. In the comment section try to mention users "@"

Actual result/Attachments

• The user list suggestion is not working.

Note: 

• Mentions continue to work in visual mode but fail to work in Text mode.

Expected result
The user list Suggestion should work when we type "@".

Version

• 7.4.1-j9