Use poetry for docs deps as well

Author: u8sand

.github/workflows/deploy-doc-to-ghpages.yml

@@ -15,9 +15,8 @@ jobs:
     - name: Install python dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install llvmlite
-        pip install -r requirements.txt
-        pip install -r docs/requirements.txt
+        pip install llvmlite poetry
+        poetry install -E docs
     - name: Building docs
       run: cd docs && make build-html
     - name: Deploy