bump to v3

codecov/codecov-action#1274 (comment)

Author: smeubank

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
         pytest --cov=api api/tests/ --cov-report=xml
 
     - name: Upload backend coverage to Codecov
-      uses: codecov/codecov-action@v4
+      uses: codecov/codecov-action@v3
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
         files: ./coverage.xml