[ci] MacOS GitHub Actions occasionally dies

[driazati]

This happens every so often during the conda setup, I'm not sure what we can really do about it:

• https://github.com/apache/tvm/runs/6560953503?check_suite_focus=true
  • https://github.com/apache/tvm/actions/runs/2373221411
    Error:

The hosted runner: GitHub Actions 6 lost communication with the server. Anything in your workflow that terminates the runner process, starves it for CPU/Memory, or blocks its network access can cause this error.

cc @Mousius @areusch @gigiblender