:umbrella: Update docs to reflect iOS 18

[sfshaza2]

https://github.com/flutter/flutter/issues/150446### Page URL

https://docs.flutter.dev/platform-integration/ios

Page source

No response

Describe the problem

The iOS 18 release is expected around mid September, after the Q3 release. Related issue:

• https://github.com/flutter/flutter/issues/150945

cc @hellohuanlin @loic

Covers:

• [x] https://github.com/flutter/website/issues/10895
• [x] https://github.com/flutter/website/issues/10902
• [x] https://github.com/flutter/website/issues/10904
• [x] https://github.com/flutter/website/issues/10894
• [x] https://github.com/flutter/website/issues/11075
• [ ] https://github.com/flutter/website/issues/10903

Expected fix

Complete referenced issues.

Additional context

No response

I would like to fix this problem.

• [ ] I will try and fix this problem on docs.flutter.dev.

[jmagman]

@sfshaza2 should there be a follow-up task to remove the iOS 18 / Xcode beta parenthetical after they are released in September?

[sethladd]

Added https://github.com/flutter/website/issues/11075 to the checkbox list above, replacing a previous item.