Updates workflow to use checkouts v4

.github/workflows/main.yml

@@ -6,7 +6,7 @@ jobs:
     name: 'Find and replace on a string'
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Run find-and-replace to remove refs/heads/
         uses: mad9000/actions-find-and-replace-string@4
         id: findandreplace