tweak(Tinebase/BroadcastHub): fix possible return values of push()

... to match return values of Redis::publish()

tine20/Tinebase/BroadcastHub.php

@@ -25,7 +25,7 @@ public function isActive(): bool
         return $this->_isActive;
     }
 
-    public function push(string $verb, string $model, string $recordId, ?string $containerId): int
+    public function push(string $verb, string $model, string $recordId, ?string $containerId): Redis|int|false
     {
         return $this->_getRedis()->publish($this->_pubSubName, json_encode([
             'verb'          => $verb,