FIX: setup fetching from branch

Author: mmcky

.github/workflows/ci.yml

@@ -76,7 +76,7 @@ jobs:
         run: |
           jb build lectures --path-output ./ -n -W --keep-going
       - name: Check for Python warnings
-        uses: QuantEcon/meta/.github/actions/check-warnings@copilot/fix-201
+        uses: QuantEcon/meta/.github/actions/check-warnings@main
         with:
           html-path: './_build/html'
           fail-on-warning: 'false'