ci: fix coverage

Author: robjtede

.github/workflows/coverage.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Upload coverage to Codecov
         uses: codecov/[email protected]
         with:
-          files: codecov.json
           fail_ci_if_error: true
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+          files: codecov.json
+          slug: bytesize-rs/bytesize
+          token: ${{ secrets.CODECOV_TOKEN }}