ci: fix poetry install

.github/workflows/workflow.yml

@@ -21,10 +21,9 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          # Patch version must be specified to avoid any cache confusion, since
-          # the cache key depends on the full Python version. Any potential
-          # difference in patches between jobs will lead to a cache not found error.
           python-version: 3.9.20
+          cache: poetry
+          cache-dependency-path: poetry.lock
 
       - name: Cache tests
         uses: actions/cache@v4
@@ -58,6 +57,9 @@ jobs:
       - name: Install Tox
         run: pipx install tox
 
+      - name: Install Poetry
+        run: pipx install poetry
+
       - name: Set up Python
         uses: actions/setup-python@v5
         with: