Remove UNSAFE_componentWillReceiveProps

Summary:
This diff removes `UNSAFE_componentWillReceiveProps` and adds the changes to `componentDidUpdate` instead.

Why use `componentDidUpdate`? When reading through the [React docs on removing UNSAFE_componentWillReceiveProps](https://reactjs.org/docs/react-component.html#unsafe_componentwillreceiveprops), it says:
> If you need to perform a side effect (for example, data fetching or an animation) in response to a change in props, use componentDidUpdate lifecycle instead.

The original usage of `UNSAFE_componentWillReceiveProps` updates the content inset when `props.contentInset` changes. However, we don't always want it to update if the content inset hasn't changed, as calling `setValue` will reset the animated value unnecessarily, and kill any current animations (which we don't want to do). [React Native doc on setValue for reference](https://reactnative.dev/docs/animatedvalue#setvalue).

Changelog:
[General] Use componentDidUpdate instead of UNSAFE_componentwillReceiveProps in ScrollView

Reviewed By: lunaleaps

Differential Revision: D26487276

fbshipit-source-id: 77419deacf5db676cd721b58f34932bd6ca2399f

Libraries/Components/ScrollView/ScrollView.js

@@ -799,19 +799,17 @@ class ScrollView extends React.Component<Props, State> {
     this._updateAnimatedNodeAttachment();
   }
 
-  UNSAFE_componentWillReceiveProps(nextProps: Props) {
+  componentDidUpdate(prevProps: Props) {
-    const currentContentInsetTop = this.props.contentInset
+    const prevContentInsetTop = prevProps.contentInset
+      ? prevProps.contentInset.top
+      : 0;
+    const newContentInsetTop = this.props.contentInset
       ? this.props.contentInset.top
       : 0;
-    const nextContentInsetTop = nextProps.contentInset
+    if (prevContentInsetTop !== newContentInsetTop) {
-      ? nextProps.contentInset.top
+      this._scrollAnimatedValue.setOffset(newContentInsetTop || 0);
-      : 0;
-    if (currentContentInsetTop !== nextContentInsetTop) {
-      this._scrollAnimatedValue.setOffset(nextContentInsetTop || 0);
     }
-  }
 
-  componentDidUpdate() {
     this._updateAnimatedNodeAttachment();
   }