[Symfony 6] Symfony\Component\HttpKernel\Event\KernelEvent::isMasterRequest() is deprecated, use isMainRequest() instead

Problem/Motivation

Error: Call to undefined method Symfony\Component\HttpKernel\Event\ResponseEvent::isMasterRequest() in Drupal\amp_optimizer\EventSubscriber\OptimizerSubscriber->optimizer() (line 93 of modules/contrib/amp_optimizer/src/EventSubscriber/OptimizerSubscriber.php).

Steps to reproduce

Update to Symfony 6

Proposed resolution

Replace the deprecated method with the replacement method.

Remaining tasks

User interface changes

API changes

Data model changes