ci: bump codecov to v4 and set the CODECOV token from the secrets

Author: bconn98

.github/workflows/coverage.yml

@@ -30,6 +30,8 @@ jobs:
         USER: "test-user"
 
     - name: Upload to codecov.io
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       with:
         fail_ci_if_error: true
+      env:
+        CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}