Firestore: Increase clock skew tolerance in FIRServerTimestampTests.mm

[dconeybe]

In FIRServerTimestampTests.mm there is a check to verify that the server timestamp values generated by the backend are within 10 seconds of the time on the local device. This, however, appears to be too aggressive, even for production. Therefore, increase the tolerance to 200 seconds.

#no-changelog

[google-oss-bot]

Coverage Report ¹

Affected Products

• FirebaseFirestore-iOS-FirebaseFirestoreInternal.framework

  Overall coverage changed from 88.09% (97fb5c2) to 88.15% (30b21fd) by +0.06%.

  Filename	Base (97fb5c2)	Merge (30b21fd)	Diff
  exception.cc	23.68%	84.21%	+60.53%
  leveldb_key.cc	98.82%	98.14%	-0.69%
  ordered_code.cc	93.90%	94.39%	+0.49%
  write_stream.cc	94.37%	91.55%	-2.82%

Test Logs

• Base (97fb5c2): https://github.com/firebase/firebase-ios-sdk/actions/runs/7172377511
• Merge (30b21fd): https://github.com/firebase/firebase-ios-sdk/actions/runs/7187363553

1. https://storage.googleapis.com/firebase-sdk-metric-reports/n1mx79tZcM.html