Update github actions/checkout from v2 to v4

https://github.com/actions/checkout/blob/main/CHANGELOG.md

Author: ericherman

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
   cibuild:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: '2.7'