Enable tests on iOS

[brianquinlan]

When enabling tests on iOS in unix_api.yml, the tests fail with:

No devices found yet. Checking for wireless devices...

No supported devices connected.

No devices are connected. Ensure that `flutter doctor` shows at least one connected device
The following devices were found, but are not supported by this project:
iPhone 16 Pro (mobile) • 8C810D0F-1949-46BE-A58D-6AE0AEEB2B52 • ios            • com.apple.CoreSimulator.SimRuntime.iOS-18-4 (simulator)
macOS (desktop)        • macos                                • darwin-arm64   • macOS 15.6.1 24G90 darwin-arm64
Chrome (web)           • chrome                               • web-javascript • Google Chrome 140.0.7339.186
If you would like your app to run on ios or macos or web, consider running `flutter create .` to generate projects for these platforms.