Try fixing ci job by updating to newer poetry version

Author: SimonCW

.github/workflows/build-docs.yml

@@ -42,8 +42,7 @@ jobs:
         # Ref: https://github.com/python-poetry/poetry-core/pull/188
         run: |
           python -m pip install --upgrade pip
-          python -m pip install --force git+https://github.com/python-poetry/poetry-core.git@ad33bc2
-          python -m pip install "poetry==1.2.0a2"
+          python -m pip install "poetry==1.5.1"
           python -m poetry plugin add poetry-version-plugin
       - name: Configure poetry
         run: python -m poetry config virtualenvs.create false