Revert "feat: add readthedocs links to pull requests"

This reverts commit 3addf1e3.

.github/workflows/docs.yml

----
-name: Add documentation links to pull requests
-
-on:
-  pull_request_target:
-    types:
-      - opened
-
-permissions:
-  pull-requests: write
-
-jobs:
-  documentation-links:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: readthedocs/actions/preview@v1
-        with:
-          project-slug: mwclient