fix: ensure membership cancellation persists

Add missing flush of the entity manager after cancelling a membership. This ensures that changes to the member's subscription details are correctly saved to the database.

src/Controller/Admin/MemberCrud.php

@@ -90,6 +90,7 @@ public function cancelMembership(AdminContext $adminContext, MollieApiClient $mo
         $subscription = $mollieApiClient->subscriptions->getFor($customer, $member->getMollieSubscriptionId());
         $subscription->cancel();
         $member->setMollieSubscriptionId(null);
+        $em = $this->getDoctrine()->getManager();
         $em->flush();
         return new Response('Membership cancelled succesfully');
     }