Cleanup workflow file

There were some leftovers that were doing no harm, but I chose to remove
them for clarity.

.github/workflows/deploy-docs.yml

@@ -1,6 +1,7 @@
 name: Deploy Docs to GitHub Pages
 
-on:  # only on changes
+on:
+  workflow_dispatch:
   push:
     branches:
       - '/v*'
@@ -8,6 +9,9 @@ on:  # only on changes
     paths:
       - 'docs/'
 
+permissions:
+  contents: write
+
 concurrency:
   group: docs
   cancel-in-progress: true
@@ -42,10 +46,3 @@ jobs:
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./docs/build
-          # The following lines assign commit authorship to the official
-          # GH-Actions bot for deploys to `gh-pages` branch:
-          # https://github.com/actions/checkout/issues/13#issuecomment-724415212
-          # The GH actions bot is used by default if you didn't specify the two fields.
-          # You can swap them out with your own user credentials.
-          user_name: github-actions[bot]
-          user_email: 41898282+github-actions[bot]@users.noreply.github.com