chore: disable CodeCov comments (#2851)

During Thursday sync, we agreed to try disabling the CodeCov comments on
PRs b/c they can be noisy. Note: the code coverage on PRs still gets
uploaded to CodeCov via `make test-coverage`

Ref: https://docs.codecov.com/docs/pull-request-comments#disable-comment

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Chores**
- Updated configuration to disable automated comments from the code
coverage tool.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/codecov.yml

@@ -0,0 +1 @@
+comment: false