[Infra] Fix flaky 'NSURLSession+GULPromises' test

[ncooke3]

A couple observations while trying to reproduce.

• The test fails in what appears to be random fashion. When it fails, it's due to an uncaught exception. I'm not sure where it's coming from but I suspect it may be OCMock related... not sure
• It seems like disabling xcpretty in the invocation increases the chance of it crashing
• It is not reproducible in Xcode
• invocation: ../firebase-ios-sdk/scripts/test_catalyst.sh GoogleUtilities test GoogleUtilities-Unit-unit

CI is green though I'm not super convinced this will work. See #120 for alt. approach that does some code cleanup.

[google-oss-bot]

Coverage Report ¹

Affected Products

No changes between base commit (c38ce36) and merge commit (637ac86).

Test Logs

• Base (c38ce36): https://github.com/google/GoogleUtilities/actions/runs/5683012891
• Merge (637ac86): https://github.com/google/GoogleUtilities/actions/runs/5778541226

1. https://storage.googleapis.com/firebase-sdk-metric-reports/m2asKcdtN0.html

[ncooke3]

I think this may be worth merging. I had a much better solution that ended up not working out in #120, so I'd like to pick from there at some point. In the meantime, an extended timeout period will hopefully reduce some flakes.

[paulb777]

Looks like this test is still failing every night in the catalyst job