Drop remnants of HHVM from tests

It was removed from Travis in c479cdd42f

tests/bootstrap.php

@@ -1,10 +1,8 @@
 <?php
 include __DIR__ . '/../vendor/autoload.php'; // composer autoload
 
-if (!defined('HHVM_VERSION')) {
-    $kernel = \AspectMock\Kernel::getInstance();
-    $kernel->init([
-        'debug' => true,
-        'includePaths' => [__DIR__ . '/../src']
-    ]);
-}
+$kernel = \AspectMock\Kernel::getInstance();
+$kernel->init([
+    'debug' => true,
+    'includePaths' => [__DIR__ . '/../src']
+]);