ci: use matrix interpreter instead of system interpreter

Author: pyoor

.github/workflows/ci.yml

@@ -69,6 +69,8 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
 
+      - run: echo "PIPX_DEFAULT_PYTHON=$(which python)" >> $GITHUB_ENV
+
       - name: Install poetry
         run: pipx install poetry