Unskip grpc template tests on macos 11

[amcasey]

There's a regression in an external library causing failures. The failures are specific to macos 11.

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.