Try newer xcode image to use newer macos

Author: jongough

.circleci/config.yml

@@ -154,7 +154,7 @@ jobs:
             install_python: false
     build-macos-universal:
         macos:
-            xcode: "14.2"
+            xcode: "15.2.0"
         environment:
             OCPN_TARGET: macos
             CMAKE_BUILD_PARALLEL_LEVEL: 2