Removing skipped test

Author: ssfinney

tests/MailRecorderTest.php

@@ -51,9 +51,6 @@ public function it_cannot_be_constructed_without_a_PHPUnit_Framework_TestCase()
      */
     public function it_cannot_be_constructed_with_class_other_than_a_PHPUnit_Framework_TestCase()
     {
-        // TODO: Skipping this until resolving PhpUnit 6 vs. 7 support
-        $this->markTestSkipped();
-
         if (class_exists(TypeError::class)) {
             try {
                 new MailRecorder(new StdClass());