graft: use double quotes for arguments

You can't use single quotes in cmd.exe. See be7ef03d7fb6.

mercurial/commands.py

@@ -4056,7 +4056,7 def graft(ui, repo, *revs, **opts):
 
       - show revisions sorted by date::
 
-          hg log -r 'sort(all(), date)'
+          hg log -r "sort(all(), date)"
 
     See :hg:`help revisions` and :hg:`help revsets` for more about
     specifying revisions.