Disable Codecov for macOS in CI

Cirrus CI is moving to M1 (arm64),
Codecov uploader still doesn't support it:
codecov/uploader#523 (comment)

.cirrus.yaml

@@ -142,7 +142,8 @@ test_task:
 
  test_script: bundle exec rspec
 
- <<: *unix_codecov
+ ## https://github.com/codecov/uploader/issues/523#issuecomment-1318842102
+ # <<: *unix_codecov
 
  - windows_container:
  image: cirrusci/windowsservercore:2019