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

Author: renovate[bot]

.github/workflows/bounty.yml

@@ -44,7 +44,7 @@ jobs:
       issues: write
     steps:
     - name: Checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
     - name: Install npm packages
       run: npm install
     - name: Sync all bounty labels
@@ -57,7 +57,7 @@ jobs:
       pull-requests: write
     steps:
     - name: Checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
     - name: Install npm packages
       run: npm install
     - name: Sync bounty labels