Summary:
After #23738 , we can add more text attributes to placeholder, so now, let's update the calculation of placeholder size based on placeholder attributes.
[iOS] [Fixed] - Fixed singleline text input placeholder size
Pull Request resolved: https://github.com/facebook/react-native/pull/23745
Differential Revision: D14320630
Pulled By: cpojer
fbshipit-source-id: 2d9e8b59ba70228202add762cfc9c6cbc77e5e95