🐛 Fix Codecov coverage uploading for the CI/CD workflow

The newest version of the codecov-action fails
to submit coverage for the CI/CD workflow,
so it isn't ready for use yet.

These changes downgrade codecov-action to v3.

.github/workflows/ci-cd.yml

@@ -367,7 +367,7 @@ jobs:
         coverage xml
       shell: bash
     - name: Send coverage data to Codecov
-      uses: codecov/codecov-action@v4
+      uses: codecov/codecov-action@v3
       with:
         files: coverage.xml
         flags: CI-GHA

CHANGES/941.contrib.rst

@@ -0,0 +1,7 @@
+`codecov-action <https://github.com/codecov/codecov-action>`_
+has been temporarily downgraded to ``v3``
+in the GitHub Actions CI/CD workflow definition
+in order to fix coverage uploading to
+`Codecov <https://app.codecov.io/gh/aio-libs/multidict>`_.
+See `this issue <https://github.com/codecov/codecov-action/issues/1252>`_
+for more details.