Remove PHPStan ignore when Drupal 11.2 is the minimum tested version

Problem/Motivation

Drupal 11.2 contains a fix for the #Call to an undefined method Drupal\\Tests\\WebAssert::(assertWait|waitFor)[a-zA-Z0-9]+\(\)# 📌 Fix PHPStan L2 error in traits Needs work PHPStan error. In order to have tests pass across multiple versions, we set reportUnmatched: false in phpstan.neon. Once 11.2 is the minimum tested version the ignore can be removed.

Remaining tasks

Remove the ignore.