Change file to files when using codecov action

This is a change required by version 5 of the action.

Author: andreasnoack

.github/workflows/ci.yml

@@ -69,4 +69,4 @@ jobs:
       - uses: codecov/codecov-action@v5
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
-          file: lcov.info
+          files: lcov.info