chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/playground.yml

@@ -24,7 +24,7 @@ jobs:
       run:
         working-directory: playground
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-node@v4
         with: