chore: fix broken link in .github/CONTRIBUTING.md

Author: RobinVdBroeck

.github/CONTRIBUTING.md

@@ -92,7 +92,7 @@ Then:
    - This will run both Node.js-based and browser-based tests.
    - Ultimately, your pull request will be built on our continuous integration servers ([GitHub Actions](https://github.com/mochajs/mocha/actions?query=workflow%3A%22Tests%22)).
      The first step to ensuring these checks pass is to test on your own machine.
-   - When tests are run in CI, a coverage check is sent to [Codecov](https://app.codecov.io/gh/mochajs/mocha. You'll need to [add the Codecov GitHub app](https://app.codecov.io/login) to upload these results from your fork. This is recommended but not necessary to open a PR.
+   - When tests are run in CI, a coverage check is sent to [Codecov](https://app.codecov.io/gh/mochajs/mocha). You'll need to [add the Codecov GitHub app](https://app.codecov.io/login) to upload these results from your fork. This is recommended but not necessary to open a PR.
      **A drop in code coverage % is considered a failed check**.
 1. Commit your changes.
    - Use a brief message on the first line, referencing a relevant issue (e.g. `closes #12345`).