Comments moderation screen:
- Don't resize the textarea when replying to long comments.
- Limit the resizing of the textarea when quick-editing long comments to 500px.
Props SergeyBiryukov, fixes #25746.

git-svn-id: https://develop.svn.wordpress.org/trunk@26550 602fd350-edb4-49c9-b593-d223f7449a82