Fix throw keyword

Author: sagikazarmark

src/PluginClient.php

@@ -138,7 +138,7 @@ private function createPluginChain($pluginList, callable $clientCallable)
         $firstCalls = 0;
         $firstCallable = function (RequestInterface $request) use ($lastCallable, &$firstCalls) {
             if ($firstCalls > $this->options['max_restarts']) {
-                return new LoopException('Too many restarts in plugin client', $request);
+                throw new LoopException('Too many restarts in plugin client', $request);
             }
 
             ++$firstCalls;