Summary:
I don't remember exactly where we talked about this but LayoutAnimation on Android is pretty stable now so there's no reason to keep it behind an experimental flag anymore. The only part that is not really stable is delete animations, so what I did is remove the default delete animation that we provide in presets.
**Test plan**
Tested that layout animations work properly without any config.
Closes https://github.com/facebook/react-native/pull/12141
Differential Revision: D4494386
Pulled By: mkonicek
fbshipit-source-id: 5dd025584e35f9bff25dc299cc9ca5c5bf5f17a3
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