Fix percentage-based border radius (#56915)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/56915

Changelog: [IOS][FIXED] Fixed percentage-based border radius

`isUniform` checks if all corners are equal, which is fine in most cases. When it comes to setting broderRadius, it also needs to be checked whether the corner is circular or not.

Reviewed By: jorge-cab, javache

Differential Revision: D105926696

fbshipit-source-id: f2d1cc7e7e2fc4a12b7964c7e06235f5a0d66bf7