Update to PHPUnit 9.6.13 and replace deprecated assertObject[Not]HasAttribute()

I forgot we didn't backport the whole deprecation-through-phpstan thingy down to 10.1.x, so the changes there are less dramatic than I expected.

I think we _really_ do want to backport down to 10.1.x though, since by suppression hard fails in 10.1.x and failing on the deprecations in 10.2.x+ we allow contrib to _not_ have support two different version for support both.

By keeping the suppression in 10.1.x only, we allow contrib to make the change, but won't make any existing test fail hard.

Thank you!

Needs rebase following the commit of Symfony 6.4.

Rerolled

Committed 3e9e43f and pushed to 11.x.

Committed d2d5cd5 and pushed to 10.2.x.

Thanks!

quietone → closed merge request !5000

Spokje → closed merge request !4999

Automatically closed - issue fixed for 2 weeks with no activity.