.github/workflows/sphinx: Add back -t pdf tag for pdf builds

Author: rkdarst

.github/workflows/sphinx.yml

@@ -102,7 +102,7 @@ jobs:
         run: |
           pip install https://github.com/rkdarst/sphinx_pyppeteer_builder/archive/refs/heads/main.zip
           #pip install sphinx_pyppeteer_builder
-          make pyppeteer
+          make SPHINXOPTS="-t pdf" pyppeteer
           mv _build/pyppeteer/*.pdf _build/dirhtml/${PDF_FILENAME}
 
       # Stage all deployed assets in _gh-pages/ for simplicity, and to