[cp][Impeller] Disable impeller_unittests

[jmagman]

impeller_unittests are flaking on flutter-3.7-candidate.1 cherry picks #39545 (comment)

These tests were turned off in #38307 to address this flake flutter/flutter#114872. Cherry-pick turning off the tests into the release branch.

Request at flutter/flutter#120640

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat (don't just cc him here, he won't see it! He's on Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[jmagman]

@godofredoc am I clear to merge this since the request has the merge-to-stable label?

[godofredoc]

@godofredoc am I clear to merge this since the request has the merge-to-stable label?

Yes, thanks for the CP, by the way Fuchsia FEMU tests should be fixed now!