Fix validate workflow not checking the current commit

Same issue as DawnbrandBots/yaml-yugi-limit-regulation@44e9297

Author: kevinlul

.github/workflows/update.yml

@@ -56,6 +56,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.ref_name }}
       - name: Duel Monsters cards do not contain Rush Duel cards (naïve check)
         run: |
           ! grep RD/ -R wikitext/Duel_Monsters_cards --include='*.yaml'