fix: correct the validation message

subcommands/logs

@@ -15,7 +15,7 @@ service-logs-cmd() {
   local cmd="$PLUGIN_COMMAND_PREFIX:logs" argv=("$@"); [[ ${argv[0]} == "$cmd" ]] && shift 1
   declare SERVICE="$1" TAIL_FLAG="$2"
 
-  [[ -z "$SERVICE" ]] && dokku_log_fail "Please specify a name for the service"
+  [[ -z "$SERVICE" ]] && dokku_log_fail "Please specify a valid name for the service"
   verify_service_name "$SERVICE"
   service_logs "$SERVICE" "$TAIL_FLAG"
 }