configitems: drop the deprecated alias for commands.update.check
experimental.updatecheck was deprecated and should have been removed once 4.4
was released. Let's drop it now.
Differential Revision: https://phab.mercurial-scm.org/D3679
graft: correct documentation about options can be reapplied
Now options --user and --date can be reapplied after we hit a conflict.
Differential Revision: https://phab.mercurial-scm.org/D3678