combine all access approval tests to run serially

[modular-magician]

Fixes #7496

I think this should fix it, although I wasn't able to reproduce it locally. I think the problem is that if these tests are run in parallel, sometimes the organization is enrolled at the beginning of the project/folder tests (showing enrolled_ancestor) and then is no longer enrolled by the end of the test, so it's no longer returned. Running them serially should fix that.

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Derived from GoogleCloudPlatform/magic-modules#4104

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