fix(ci): update codecov-action to v5 (#114)

* fix(ci): update `codecov-action` for tokenless uploads

- per https://docs.codecov.com/docs/codecov-tokens#uploading-without-a-token, it seems a newer version is required now

* token is apparently needed for `main` and other "unprefixed" branches

- c.f. https://docs.codecov.com/docs/codecov-tokens#tokenless-on-unprotected-branches

* remove token and change Codecov settings

apparently according to https://docs.codecov.com/docs/codecov-tokens#enabling-tokenless-uploads-for-public-repositories, there is a setting to enable this, however the setting itself does not say "public repos only" confusingly....

(cherry picked from commit 599f371)

.github/workflows/ci.yml

@@ -30,4 +30,4 @@ jobs:
     - name: Test w/ coverage report
       run: npm run test:coverage
     - name: Upload coverage report to Codecov
-      uses: codecov/codecov-action@v2
+      uses: codecov/codecov-action@v5