ci: bump actions/checkout to v6 (credentials moved to RUNNER_TEMP)

Author: ph33nx

.github/workflows/release.yml

@@ -20,7 +20,7 @@ jobs:
       contents: write
       id-token: write
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           token: ${{ secrets.GITHUB_TOKEN }}