chore(internal): use actions/checkout@v4 for codeflow (#270)

.github/workflows/release-doctor.yml

@@ -10,7 +10,7 @@ jobs:
     if: github.repository == 'lithic-com/lithic-go' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch' || startsWith(github.head_ref, 'release-please') || github.head_ref == 'next')
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Check release environment
         run: |