Revert "Bump codecov/codecov-action from 3 to 4 (#618)" (#630)

This reverts commit 8fcdd11.

Author: viceroypenguin

.github/workflows/build.yml

@@ -36,4 +36,4 @@ jobs:
       run: dotnet test -c Release --no-build --logger GitHubActions
 
     - name: Upload coverage reports to Codecov with GitHub Action
-      uses: codecov/codecov-action@v4
+      uses: codecov/codecov-action@v3