Fix tests temporarily by temporarily removing memory limit

According to laravel/framework#30736, there is
a confirmed memory leak in php (https://bugs.php.net/bug.php?id=76982)
that causes memory usage in PHPUnit tests to go up steadily. Everyone is
waiting for PHP to fix this, but in the meantime, we can still run our
tests by removing the PHP memory limit. Sooner or later, when adding
more tests, we might run into the container's memory limits though...
Hopefully the PHP bug will be fixed by then.

tests/TestCase.php

@@ -25,6 +25,7 @@ abstract class TestCase extends BaseTestCase {
 
     public function setUp(): void {
         Dotenv::createImmutable(__DIR__.'/../', '.env.testing')->load();
+        ini_set('memory_limit', '-1');
 
         parent::setUp();