Do not cast file_put_contents's return type

If $lock->value was an empty string, this would fix a bug, but it never
is, it is a uniqid-generated string.

src/Cache/Region/FileLockRegion.php

@@ -176,7 +176,7 @@ public function lock(CacheKey $key): Lock|null
         $lock     = Lock::createLockRead();
         $filename = $this->getLockFileName($key);
 
-        if (! @file_put_contents($filename, $lock->value, LOCK_EX)) {
+        if (@file_put_contents($filename, $lock->value, LOCK_EX) === false) {
             return null;
         }