Disable DoNotMock Error Prone check

Recent Bazel upgrades Error Prone to major version 2.4.0, that is much
stricter now. In addition, starting from guava 29.0-jre, Cache class was
annotated with DoNotMock Error Prone annotation: [1].

Disable the bug pattern, because without using the mock as advertized by
the check would break the corresponding mockito verifications.

[1] https://github.com/google/guava/commit/4eea0f79c27864039a653ec4ca09ef7585e439fc

Change-Id: Ia118ef9eb0c0adb1480488a7b97a0d77a7b31322