[native] Increase clickable region of ColorSelector Save button

Summary:
Quick fix before finalizing ColorSelector. Noticed a bug where the "Save" button in the ColorSelector was only being clicked when clicking on the "Save" text, and not anywhere on the button.

Fixed this by removing the outer View container and replacing it with a TouchableOpacity, allowing the entire region to be clickable and execute the onPress function.

What it looks like now:

Test Plan: Looks and works as expected on iOS.

Reviewers: atul, palys-swm

Reviewed By: atul, palys-swm

Subscribers: ashoat, Adrian

Differential Revision: https://phab.comm.dev/D4415