Update codecov/codecov-action action to v4

Author: renovate[bot]

.github/workflows/rav1e.yml

@@ -277,7 +277,7 @@ jobs:
           sccache --stop-server
       - name: Codecov upload
         if: matrix.conf == 'grcov-codecov'
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
         with:
           files: lcov.info