Bump actions/checkout to v3

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

Author: illia-v

.github/workflows/ensurepip_verify_bundled.yml

@@ -13,7 +13,7 @@ jobs:
   verify:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Compare checksums of bundled pip and setuptools to ones published on PyPI
         run: |
           package_names=("pip" "setuptools")