chore(deps): update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/buildtest.yml

@@ -10,7 +10,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3.0.2
+    - uses: actions/checkout@v4.1.1
     - uses: actions/[email protected]
       with:
          node-version: '18.x'