Avoid calling deprecated Type::getName() (doctrine#6359)

Follow-up to doctrine#6358 (@sbuerk): `getName()` is gone on 4.0.x. This change
will make merging this test up easier for us.

tests/Functional/Schema/PostgreSQLSchemaManagerTest.php

@@ -310,7 +310,7 @@ public function testJsonDefaultValue(): void
 
         $columns = $this->schemaManager->listTableColumns('test_json');
 
-        self::assertSame(Types::JSON, $columns['foo']->getType()->getName());
+        self::assertSame(Type::getType(Types::JSON), $columns['foo']->getType());
         self::assertSame('{"key": "value with a single quote \' in string value"}', $columns['foo']->getDefault());
     }