ci: update macOS runner from unsupported macos-13 to macos-latest (#13855)

- Replace deprecated `macos-13` with `macos-latest` runner
- Ensure CI compatibility with supported macOS versions
- Maintain build stability and future-proof workflows

.github/workflows/flutter-build.yml

@@ -444,7 +444,7 @@ jobs:
           - {
               arch: aarch64,
               target: aarch64-apple-ios,
-              os: macos-13,
+              os: macos-latest,
               vcpkg-triplet: arm64-ios,
             }
     steps: