Investigate flaky `GULNetworkTests`

[ncooke3]

While publishing the 7.11.0 pod, the podspec failed to validate. Further investigation showed that something about the GULNetworkTests is causing flakes. They flakes seem to emerge depending on the Xcode version. Flakes were reproducible on Xcode 14.2.

Steps to reproduce:

1. pod gen GoogleUtilities.podspec --platforms=macos
2. Navigate to GULNetworkTests.m
3. Right-click the testing icon on GULNetworkTests and run the test repeatedly (~100 times should be fine)