Comments: Restore global $comment assignment in comment_form_title().

Restores the global `$comment` assignment in `comment_form_title()`, which was mistakely removed in [55369].

As noted in the function's DocBlock:
{{{
@internal The $comment global must be present to allow template tags access to the current comment. See https://core.trac.wordpress.org/changeset/36512.
}}}

Follow-up to [55369].

Props hellofromTonya, costdev.
Fixes #53962.
Built from https://develop.svn.wordpress.org/trunk@55395


git-svn-id: http://core.svn.wordpress.org/trunk@54928 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.2-beta2-55394';
+$wp_version = '6.2-beta2-55395';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.