Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/push_gem.yml

@@ -22,7 +22,7 @@ jobs:
         with:
           egress-policy: audit
 
-      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v5.0.1
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
       - name: Set up Ruby
         uses: ruby/setup-ruby@cacc9f1c0b3f4eb8a16a6bb0ed10897b43b9de49 # v1.176.0
         with: