Get rid of unofficial GH actions to install poetry (#10)

Author: dannywillems

.github/workflows/actions.yml

@@ -15,10 +15,8 @@ jobs:
       - uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
-      - name: Run image
-        uses: abatilo/actions-poetry@v2.0.0
-        with:
-          poetry-version: ${{ matrix.poetry-version }}
+      - name: Install poetry
+        run: pip install poetry==${{ matrix.poetry-version}}
       - name: View poetry --help
         run: poetry --help
       - name: Install deps