CI: switch iOS build to macos-14 runner as macos-latest currently fails.

.github/workflows/build.yml

@@ -558,7 +558,7 @@ jobs:
       run: xcodebuild -project examples/example_apple_opengl2/example_apple_opengl2.xcodeproj -target example_osx_opengl2
 
   iOS:
-    runs-on: macos-latest
+    runs-on: macos-14
     steps:
     - uses: actions/checkout@v4