Fix "Redefinition of parameter $_" error in PHP7

Author: jsor

tests/React/Promise/PromiseTest.php

@@ -51,7 +51,7 @@ public function shouldResolve()
     /** @test */
     public function shouldReject()
     {
-        $promise = new Promise(function($_, $reject) {
+        $promise = new Promise(function($resolve, $reject) {
             $reject(1);
         });
 
@@ -67,7 +67,7 @@ public function shouldReject()
     /** @test */
     public function shouldProgress()
     {
-        $promise = new Promise(function($_, $_, $progress) use (&$notify) {
+        $promise = new Promise(function($resolve, $reject, $progress) use (&$notify) {
             $notify = $progress;
         });