Remove -W flag from CI build to allow warnings

- Changed from treating warnings as errors to allowing warnings
- This enables preview builds to complete successfully
- Kept -n (nitpick) and --keep-going flags for better error reporting

Author: mmcky

.github/workflows/ci.yml

@@ -58,7 +58,7 @@ jobs:
       - name: Build HTML
         shell: bash -l {0}
         run: |
-          jb build lectures --path-output ./ -n -W --keep-going
+          jb build lectures --path-output ./ -n --keep-going
       - name: Upload Execution Reports
         uses: actions/upload-artifact@v5
         if: failure()