update: use single quotes in use warning

mercurial/destutil.py

@@ -416,8 +416,8 b' def _statusotherbranchheads(ui, repo):'
                         'updating to a closed head\n') %
                       (currentbranch))
             if otherheads:
-                ui.warn(_('(committing will reopen the head, '
-                            'use `hg heads .` to see %i other heads)\n') %
+                ui.warn(_("(committing will reopen the head, "
+                            "use 'hg heads .' to see %i other heads)\n") %
                           (len(otherheads)))
             else:
                 ui.warn(_('(committing will reopen branch "%s")\n') %

tests/test-update-branches.t

@@ -195,7 +195,7 b' if on the closed branch head:'
   $ norevtest "on closed branch head" clean 6
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
   no open descendant heads on branch "default", updating to a closed head
-  (committing will reopen the head, use `hg heads .` to see 1 other heads)
+  (committing will reopen the head, use 'hg heads .' to see 1 other heads)
   parent=6
 
 if descendant non-closed branch head exists, and it is only one branch head:
@@ -214,7 +214,7 b' if all descendant branch heads are close'
   $ norevtest "all descendant branch heads are closed" clean 3
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
   no open descendant heads on branch "default", updating to a closed head
-  (committing will reopen the head, use `hg heads .` to see 1 other heads)
+  (committing will reopen the head, use 'hg heads .' to see 1 other heads)
   parent=6
 
 Test updating if all branch heads are closed