Update PR workflow to use Xcode 16.4 (#7060)

Author: kraenhansen

.github/workflows/pr-realm-js.yml

@@ -492,7 +492,7 @@ jobs:
       - generate-jsi
       - prebuild-apple
     env:
-      DEVELOPER_DIR: /Applications/Xcode_15.4.app
+      DEVELOPER_DIR: /Applications/Xcode_16.4.app
       IOS_DEVICE_NAME: iPhone 15
       # See https://guides.cocoapods.org/using/faq.html#can-i-change-the-default-cocoapods-repositories-folder
       CP_HOME_DIR: ${{ github.workspace }}/.cocoapods