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

Author: renovate[bot]

.github/workflows/publish.yml

@@ -13,7 +13,7 @@ jobs:
       # IMPORTANT: this permission is mandatory for trusted publishing
       id-token: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: pdm-project/setup-pdm@v4