comments: Fix an incorrent DOM element selection.

This commit fixes a bug that was causing text from previously edited
comment to get saved when two comments were edited one after other.
Text area with id of `#content` isn't unique on the page but it was
being treated as unique by the event handling code.

Fixes: go-gitea#5581.

public/js/index.js

@@ -690,7 +690,7 @@ function initRepository() {
             // Setup new form
             if ($editContentZone.html().length == 0) {
                 $editContentZone.html($('#edit-content-form').html());
-                $textarea = $('#content');
+                $textarea = $editContentZone.find('textarea');
                 issuesTribute.attach($textarea.get());
                 emojiTribute.attach($textarea.get());