Remove an unused argument.

HttpCache/HttpCache.php

@@ -522,7 +522,7 @@ protected function isFreshEnough(Request $request, Response $entry)
     protected function lock(Request $request, Response $entry)
     {
         // try to acquire a lock to call the backend
-        $lock = $this->store->lock($request, $entry);
+        $lock = $this->store->lock($request);
 
         // there is already another process calling the backend
         if (true !== $lock) {