send-pack: unify error messages for unsupported capabilities

If --signed is not supported, the error message names the remote
"receiving end". If --atomic is not supported, the error message
names the remote "server". Unify the naming to "receiving end"
as we're in the context of "push".

Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

send-pack.c

@@ -360,7 +360,7 @@ int send_pack(struct send_pack_args *args,
 		return 0;
 	}
 	if (args->atomic && !atomic_supported)
-		die(_("server does not support --atomic push"));
+		die(_("the receiving end does not support --atomic push"));
 
 	use_atomic = atomic_supported && args->atomic;