Allow comment.php?action=editcomment to be accessible for a comment that is...

Allow comment.php?action=editcomment to be accessible for a comment that is spam. props josephscott, fixes #19977, see #18340.

git-svn-id: https://core.svn.wordpress.org/trunk@19856 1a063a9b-81f0-0310-95a4-ce76da25c4cd