ci: bump macos version to xcode 15.4.0

Author: jiegec

.circleci/config.yml

@@ -119,7 +119,7 @@ jobs:
             nix-build
   macos:
     macos:
-      xcode: 14.3.1
+      xcode: 15.4.0
     steps:
       - checkout
       - run: