Update checkout action version to v6

Author: jackspiering

.github/workflows/contributors.yml

@@ -18,7 +18,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Update contributors in README
         uses: akhilmhdh/contributors-readme-action@v2.3.11
@@ -29,4 +29,4 @@ jobs:
           use_username: true
           commit_message: "docs(contributors): update README contributors"
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}