Summary:
Follow-up to https://github.com/facebook/react-native/pull/19809
This fix generalizes the `setAttributedString:` fix to single-line text fields.
Fixes#19339
_Pull requests that expand test coverage are more likely to get reviewed. Add a test case whenever possible!_
Pull Request resolved: https://github.com/facebook/react-native/pull/22546
Differential Revision: D13948951
Pulled By: shergin
fbshipit-source-id: 67992c02b32f33f6d61fac4554e4f46b973262c1