Fixed typo in Github action.

Author: madpah

.github/workflows/poetry.yml

@@ -35,7 +35,7 @@ jobs:
         # see https://github.com/actions/setup-python
         uses: actions/setup-python@v2
         with:
-          python-version: {{ matrix.python-version }}
+          python-version: ${{ matrix.python-version }}
           architecture: 'x64'
       - name: Install poetry
         # see https://github.com/marketplace/actions/setup-poetry