Fix get signals for run round robin consumer if pcntl not installed.

Author: ZhukV

src/Command/RunRoundRobinConsumerCommand.php

@@ -37,6 +37,10 @@ public function __construct(private readonly RoundRobinConsumer $consumer)
      */
     public function getSubscribedSignals(): array
     {
+        if (!\function_exists('pcntl_signal')) {
+            return [];
+        }
+
         return [
             \SIGINT,
             \SIGTERM,