Summary:
This pull request aims to remove iOS 11 availability check which is no longer needed.
The minimum iOS deployment target for React Native is iOS 11 but we still have iOS 11 version check like below.
```
if (available(iOS 11.0, *)) {
```
This is a continuation pull request of https://github.com/facebook/react-native/pull/32151
## Changelog
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https://github.com/facebook/react-native/wiki/Changelog
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[iOS] [Changed] - Remove iOS 11 availability check
Pull Request resolved: https://github.com/facebook/react-native/pull/32488
Reviewed By: yungsters
Differential Revision: D32006312
Pulled By: ryancat
fbshipit-source-id: 0ee6579e433a15d3d220a52d2ccd6931b0513971
9b059b6709