xcode 15.0.1 which seems to be the oldest supported

Author: langleyd

.github/workflows/swift.yml

@@ -20,7 +20,7 @@ jobs:
 
     - uses: maxim-lobanov/setup-xcode@v1
       with:
-        xcode-version: '14.3.1'
+        xcode-version: '15.0.1'
 
     - name: Install Swift
       uses: swift-actions/setup-swift@v2