stack: remove unnecessary reverse() predicate
Stack already sorts revisions, so no need to do it twice.
This change was a part of D2400, which didn't land for other reasons. See also
D2399, where this change was suggested.
Differential Revision: https://phab.mercurial-scm.org/D6706
#require docutils gettext
$ $TESTDIR/check-gendoc de
checking for parse errors
Die Dateien werden dem Projektarchiv beim n\xc3\xa4chsten \xc3\x9cbernehmen (commit) hinzugef\xc3\xbcgt. Um dies vorher r\xc3\xbcckg\xc3\xa4ngig zu machen, siehe:hg:`forget`. (esc)
warning: please have a space before :hg: