Install Poetry for check-pr action

.github/workflows/check-pr.yaml

@@ -21,7 +21,7 @@ jobs:
         uses: hellofresh/action-changed-files@v2
         with:
           pattern: src/(?P<package>[^/]+)/
-
+    
   check-root:
     name: Check root
     runs-on: ubuntu-20.04
@@ -33,6 +33,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v3
 
+      - name: Install Poetry
+        uses: snok/install-poetry@v1
+
       - name: Install dependencies
         run: |
           make ci-init