Bump codecov/codecov-action from 3 to 4

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 3 to 4.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md)
- [Commits](codecov/codecov-action@v3...v4)

---
updated-dependencies:
- dependency-name: codecov/codecov-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/codecov.yml

@@ -20,6 +20,6 @@ jobs:
       run: make dependencies || true # Used in fortio for instance to prep for go tests
     - name: Run test coverage
       run: go test -coverprofile=coverage.out ./...
-    - uses: codecov/codecov-action@v3
+    - uses: codecov/codecov-action@v4
       with:
         files: coverage.out