Add default case to death test AssumeRole() switch

Meta has -Wswitch-default enabled for large parts of the repository.
This warning requires a default case to cover non-exhaustive enumeration
handling. This adds a default case that logs a fatal error for any
unexpected AssumeRole() return value.

googletest/include/gtest/internal/gtest-death-test-internal.h

@@ -244,6 +244,8 @@ GTEST_API_ bool ExitedUnsuccessfully(int exit_status);
           gtest_dt->Abort(::testing::internal::DeathTest::TEST_DID_NOT_DIE);   \
           break;                                                               \
         }                                                                      \
+        default:                                                               \
+          GTEST_LOG_(FATAL) << "Unexpected AssumeRole() return value.";        \
       }                                                                        \
     }                                                                          \
   } else                                                                       \