completion: allow 'git remote' subcommand completion

After typing 'git remote ', the subcommand options were not shown. Fix it
by adding the missing __gitcomp call.
Signed-off-by: NDan McGee <dpmcgee@gmail.com>
Acked-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -1052,6 +1052,7 @@ _git_remote ()
 	local subcommands="add rm show prune update"
 	local subcommand="$(__git_find_subcommand "$subcommands")"
 	if [ -z "$subcommand" ]; then
+		__gitcomp "$subcommands"
 		return
 	fi