Oops, fix typo

Author: eemeli

.github/workflows/deploy.yml

@@ -20,7 +20,7 @@ jobs:
       MDBOOK_VERSION: v0.4.36
     steps:
       - name: Clone repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
       - name: Install mdbook
         run: |
           mkdir installed-bins