ci: fix deprecated codecov argument

Author: cakebaker

.github/workflows/ci.yml

@@ -126,7 +126,7 @@ jobs:
       uses: codecov/codecov-action@v5
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
-        file: ${{ steps.coverage.outputs.report }}
+        files: ${{ steps.coverage.outputs.report }}
         ## flags: IntegrationTests, UnitTests, ${{ steps.vars.outputs.CODECOV_FLAGS }}
         flags: ${{ steps.vars.outputs.CODECOV_FLAGS }}
         name: codecov-umbrella