ci: fix codecov-action arg name

Author: inkydragon

.github/workflows/CI.yml

@@ -48,7 +48,7 @@ jobs:
         with:
           token: ${{ secrets.CODECOV_TOKEN }} # required
           fail_ci_if_error: true
-          file: lcov.info
+          files: lcov.info
 
   docs:
     name: Documentation