Add iOS 18.4 beta warnings

[loic-sharma]

iOS 18.4 beta breaks Flutter's debug mode on physical devices. Until we hotfix this issue, users should not upgrade to iOS 18.4 beta. Users that have upgraded their device to iOS 18.4 beta should run their apps in release or profile modes, or, target an iOS simulator instead.

This PR will be reverted once the issue is hotfixed.

Part of flutter/flutter#163984

Screenshots

https://flutter-docs-prod--pr11740-ios-18-4-warning-45b6gmsm.web.app/get-started/install/macos/mobile-ios#configure-your-target-ios-device

https://flutter-docs-prod--pr11740-ios-18-4-warning-45b6gmsm.web.app/platform-integration/ios/ios-latest

Presubmit checklist

• This PR is marked as draft with an explanation if not meant to land until a future stable release.
• This PR doesn’t contain automatically generated corrections (Grammarly or similar).
• This PR follows the Google Developer Documentation Style Guidelines — for example, it doesn’t use i.e. or e.g., and it avoids I and we (first person).
• This PR uses semantic line breaks of 80 characters or fewer.

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit 4f514c3):

https://flutter-docs-prod--pr11740-ios-18-4-warning-45b6gmsm.web.app

[jmagman]

Content LGTM, tech writer should approve and wordsmith as needed though.

[cbracken]

LGTM with a tiny suggestion for wording.

[RedBrogdon]

WDYT of:

An upcoming change to iOS has caused a temporary break in Flutter's ability to debug code on physical devices running iOS 18.4 (currently in beta). See [flutter#163984][] for details.

In the meantime, we recommend these workarounds:

• When developing with a physical device, use one running iOS 18.3 or earlier.
• Use a simulator for development rather than a physical device.
• If you must use a device updated to iOS 18.4, use [Flutter's release or profile build modes][] to do so.

[loic-sharma]

Updated with some minor tweaks!

[loic-sharma]

I'll go ahead and merge this since this is a higher priority update.

[gnprice]

This link seems to be wrong — it ends up pointing to https://github.com/ios/ios-latest .

[loic-sharma]

Thanks for catching this, opened: #11752