Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/cd.yml

@@ -8,7 +8,7 @@ jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v2
       - name: Build and publish to pypi
         uses: JRubics/poetry-publish@v1.16