chore: bump checkout action to v6

Author: jonasnobile

.github/workflows/ci.yml

@@ -84,7 +84,7 @@ jobs:
           --health-retries 20
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: oven-sh/setup-bun@v2
 
       - run: bun install --frozen-lockfile