Update codecov/codecov-action action to v6

| datasource  | package                | from   | to     |
| ----------- | ---------------------- | ------ | ------ |
| github-tags | codecov/codecov-action | v5.5.4 | v6.0.0 |

Author: renovate[bot]

.github/workflows/mutation-tests.yml

@@ -58,4 +58,6 @@ jobs:
         run: "make infection PHPUNIT_FLAGS=--coverage-clover=coverage.xml"
 
       - name: "Upload Code Coverage"
-        uses: "codecov/codecov-action@v5.5.4"
+        uses: "codecov/codecov-action@v6.0.0"
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}