use build_sphinx_docs action w/o requirements.txt

Author: niksirbi

.github/workflows/docs_build_and_deploy.yml

@@ -27,7 +27,9 @@ jobs:
     name: Build Sphinx Docs
     runs-on: ubuntu-latest
     steps:
-      - uses: neuroinformatics-unit/actions/build_sphinx_docs@v2
+      - uses: neuroinformatics-unit/actions/build_sphinx_docs@smg/doc-dependencies-as-extra
+        with:
+          use-requirementstxt: false
 
   deploy_sphinx_docs:
     name: Deploy Sphinx Docs