Merge pull request #1617 from macvim-dev/dependabot/github_actions/actions/checkout-6

CI: Bump actions/checkout from 5 to 6

Author: ychin

.github/workflows/macvim-buildtest.yaml

@@ -64,7 +64,7 @@ jobs:
     runs-on: ${{ inputs.os }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up legacy build
         if: inputs.legacy