Fix and re-enable playmode tests

[daniellovell]

playmode tests in the test.yaml GitHub Actions flow were disabled since they seemed to not be repeatable.
Often they will time out when running on the GitHub runner, causing a failure. Whereas when run locally they would complete successfully.

[tryuan99]

Are the playmode tests still disabled?

[daniellovell]

Yea they're still disabled. I've got the general feeling that performance has worsened lately, so it's even less likely now that they will reproducibly pass in the Runner.

Probably worth trying again though after our Unity update. I'll look into this.