Try xcode 15

Author: langleyd

.github/workflows/swift.yml

@@ -18,6 +18,10 @@ jobs:
     steps:
     - uses: actions/checkout@v3
 
+    - uses: maxim-lobanov/setup-xcode@v1
+      with:
+        xcode-version: '15.4'
+
     - name: Install Swift
       uses: swift-actions/setup-swift@v2
       with: