Use swift 6.0 in windows CI

Author: adam-fowler

.github/workflows/ci.yml

@@ -64,7 +64,7 @@ jobs:
     steps:
       - uses: compnerd/gha-setup-swift@main
         with:
-          branch: swift-5.10-release
-          tag: 5.10-RELEASE
+          branch: swift-6.0-release
+          tag: 6.0-RELEASE
       - uses: actions/checkout@v4
       - run: swift test