Avoid catching AssertionError for actual failures.

ActivityManagerServiceUtilsTest was checking to make sure its test
method would actually validate input and correctly fail. Unfortunately,
it also caught the AssertionError for the test _actually_ failing.

Bug: 217923092
Test: errorprone build
      ActivityManagerUtilsTest#testCheckShouldSamplePackage
Change-Id: Icd5a62c470b0f3d15de65f4b43d4355ba9c4661c