Remove unused message 'resetpass'
This was (unintentionally?) replaced by 'changepassword' in r86280
(1a80d4637002), which renamed the special page from Special:ResetPass
'changepassword' was previously used in Special:Preferences until
r49790 (155ddf6de4a2) for a heading directly above the link to
I moved messages 'changepassword' and 'changepassword-summary' to
the correct blocks in MessagesEn.php and messages.inc and also
updated message documentation that referred to Special:ResetPass.