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

mercurial/stack.py

@@ -22,7 +22,7 b' def getstack(repo, rev=None):'
     if rev is None:
         rev = '.'
 
-    revspec = 'reverse(only(%s) and not public() and not ::merge())'
+    revspec = 'only(%s) and not public() and not ::merge()'
     revset = revsetlang.formatspec(revspec, rev)
     revisions = scmutil.revrange(repo, [revset])
     revisions.sort()