API Update use statements to match changes in framework

src/Context/EmailContext.php

@@ -10,7 +10,7 @@
 use SilverStripe\BehatExtension\Utility\TestMailer;
 use SilverStripe\Core\Injector\Injector;
 use Symfony\Component\DomCrawler\Crawler;
-use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Contracts\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\Mailer\MailerInterface;
 use Symfony\Component\Mailer\Transport\NullTransport;
 
@@ -50,6 +50,7 @@ public function before(BeforeScenarioScope $event)
     {
         // Also set through the 'supportbehat' extension
         // to ensure its available both in CLI execution and the tested browser session
+        /** @var EventDispatcherInterface $dispatcher */
         $dispatcher = Injector::inst()->get(EventDispatcherInterface::class . '.mailer');
         $transport = new NullTransport($dispatcher);
         $this->mailer = new TestMailer($transport, $dispatcher);

src/Utility/TestMailer.php

@@ -4,7 +4,7 @@
 
 use InvalidArgumentException;
 use SilverStripe\Control\Email\Email;
-use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Contracts\EventDispatcher\EventDispatcherInterface;
 use SilverStripe\Dev\TestMailer as BaseTestMailer;
 use SilverStripe\TestSession\TestSessionEnvironment;
 use Symfony\Component\Mailer\Envelope;