(standards): fix coding standards issue, remove extra whitespace.

Author: StyxOfDynamite

src/FcmMessage.php

@@ -82,7 +82,7 @@ public function data(?array $data): self
     {
         if (! empty(array_filter($data, fn($value) => ! is_string($value)))) {
             throw new \InvalidArgumentException('Data values must be strings.');
-          }
+        }
 
         $this->data = $data;