swift-button-functional-test job failing due to changes in sign in flow

[mdmathias]

The swift-button-functional-test job appears to no longer pass, likely due to changes in the sign in flow. I was able to get parts of the test case to pass, but not reliably. Running locally on a simulator, I would occasionally see the sign in flow succeed, and other times I would see a screen telling me that Safari was unable to contact the server.

Since this test is not passing, and is blocking the beta release of AppCheck support within GSI, I am going to disable this job. This is not harmful since this test is completely unrelated to AppCheck, and the AppCheck tests (including integration) are passing.

We should nonetheless follow up on this and fix the issue.

[mdmathias]

Need to make sure to re-enable this test and revert the if check back to if: "!github.event.pull_request.head.repo.fork".