fix predis clear() when using redis 7.4 (#1522)

Author: vintagesucks

src/Repositories/RedisMetricsRepository.php

@@ -390,7 +390,7 @@ public function clear()
 
             do {
                 [$cursor, $keys] = $this->connection()->scan(
-                    $cursor, ['match' => config('horizon.prefix').$pattern]
+                    $cursor ?? 0, ['match' => config('horizon.prefix').$pattern]
                 );
 
                 foreach ($keys ?? [] as $key) {