CI: Fix up doc deployment

Descope permissions and replace use of non-existent deploy key. This
should work fine with a GitHub token now.

.github/workflows/docs.yml

@@ -10,9 +10,6 @@ on:
       - v[0-9]+.[0-9]+.[0-9]+
   pull_request:
 
-permissions:
-  contents: write
-
 concurrency:
   group: ${{ github.workflow}}-${{ github.head_ref }}
   cancel-in-progress: true
@@ -68,6 +65,8 @@ jobs:
     runs-on: ubuntu-latest
     env:
       DOC_VERSION: dev
+    permissions:
+      contents: write
 
     steps:
     - name: Download doc build
@@ -85,7 +84,7 @@ jobs:
     - name: Upload to GitHub Pages
       uses: peaceiris/actions-gh-pages@v4
       with:
-        deploy_key: ${{ secrets.GHPAGES_DEPLOY_KEY }}
+        github_token: ${{ secrets.GITHUB_TOKEN }}
         publish_dir: ./docs/build/html
         exclude_assets: '.buildinfo,_static/jquery-*.js,_static/underscore-*.js'
         destination_dir: ./${{ env.DOC_VERSION }}