completion: complete "unstuck" `git push --recurse-submodules`

Since the argument to `--recurse-submodules` is mandatory, it does not
need to be stuck to the option with `=`.

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -1617,6 +1617,11 @@ _git_push ()
 	--repo)
 		__gitcomp_nl "$(__git_remotes)"
 		return
+		;;
+	--recurse-submodules)
+		__gitcomp "$__git_push_recurse_submodules"
+		return
+		;;
 	esac
 	case "$cur" in
 	--repo=*)