zsh: remove deprecated -f option for hg update

zsh: remove deprecated -f option for hg update

--- a/contrib/zsh_completion	Wed Dec 06 12:45:27 2006 -0600
+++ b/contrib/zsh_completion	Tue Dec 05 21:30:04 2006 -0600
@@ -619,7 +619,6 @@
 _hg_cmd_update() {
   _arguments -s -w : $_hg_global_opts \
   '(--clean -C)'{-C,--clean}'[overwrite locally modified files]' \
-  '(--force -f)'{-f,--force}'[force a merge with outstanding changes]' \
   ':revision:_hg_tags'
 }