[JIRAALIGN-1579] Announcements character limit is blocking

Issue Summary

Announcements character limit is too small–cannot use this feature effectively at its current limit. 

Steps to Reproduce

1. Add announcement over 400 characters
2. See limitation

Expected Results

Should support up to 4000 characters which equates to about 1 page, single-spaced, of text. The announcement modal should expand to fit text. If text is too long for screen, add scroll bar to modal

Actual Results

Supports only 400 characters.

Workaround

No workaround.