FLAKE: //test/core/slice/slice_test.exe is flaky on windows RBE opt #20519
Description
Seems to be failing with the opt config https://source.cloud.google.com/results/invocations/5322bbef-9cde-4065-9192-66c6817ca729/targets/%2F%2Ftest%2Fcore%2Fslice:slice_test/log in all builds.