ci: upgrade Windows to Swift 6.1

- Update from Swift 6.0 to 6.1 for Windows CI
- Use new 'swift-version' parameter instead of deprecated 'branch'/'tag'
- May resolve cyclic dependency issue in Swift 6.0 Windows toolchain

Author: coenttb

.github/workflows/ci.yml

@@ -58,15 +58,14 @@ jobs:
         run: swift test
 
   windows:
-    name: Windows (Swift 6.0)
+    name: Windows (Swift 6.1)
     runs-on: windows-latest
     steps:
       - uses: actions/checkout@v5
 
       - uses: compnerd/gha-setup-swift@main
         with:
-          branch: swift-6.0-release
-          tag: 6.0-RELEASE
+          swift-version: "6.1"
 
       - name: Build
         run: swift build