update github action

Author: jbigot

.github/workflows/deploy.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout master
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
       with: { fetch-depth: 0 }
     - name: Checkout gh-pages
       run: git worktree add -B gh-pages public remotes/origin/gh-pages