remove unused suppressions in xplat

Summary:
Removes unused suppressions before deploying 0.91. See D13708161 for more context on why these couldn't be removed before.

I will follow up with 2 more diffs:
1. A diff that bumps the flow version in xplat and removes unused suppressions
2. A diff that adds new suppressions for 0.91

Reviewed By: samwgoldman

Differential Revision: D13720219

fbshipit-source-id: b07dd163962fed7ff27ce3e0a4a73a71c51965d9

Libraries/Components/DatePicker/DatePickerIOS.ios.js

@@ -117,7 +117,6 @@ class DatePickerIOS extends React.Component<Props> {
     mode: 'datetime',
   };
 
-  // $FlowFixMe How to type a native component to be able to call setNativeProps
   _picker: ?React.ElementRef<typeof RCTDatePickerNativeComponent> = null;
 
   componentDidUpdate() {

Libraries/Components/ScrollView/ScrollView.js

@@ -761,7 +761,6 @@ class ScrollView extends React.Component<Props, State> {
   }
 
   _getKeyForIndex(index, childArray) {
-    // $FlowFixMe Invalid prop usage
     const child = childArray[index];
     return child && child.key;
   }

RNTester/js/ListViewPagingExample.js

@@ -88,7 +88,6 @@ class Thumb extends React.Component<{}, $FlowFixMeState> {
 }
 
 class ListViewPagingExample extends React.Component<$FlowFixMeProps, *> {
-  // $FlowFixMe found when converting React.createClass to ES6
   constructor(props) {
     super(props);
     const getSectionData = (dataBlob, sectionID) => {

RNTester/js/RNTesterExampleList.js

@@ -20,8 +20,6 @@ const RNTesterActions = require('./RNTesterActions');
 const RNTesterExampleFilter = require('./RNTesterExampleFilter');
 const View = require('View');
 
-/* $FlowFixMe(>=0.78.0 site=react_native_android_fb) This issue was found when
- * making Flow check .android.js files. */
 import type {RNTesterExample} from 'RNTesterTypes';
 import type {ViewStyleProp} from 'StyleSheet';
 
@@ -71,9 +69,6 @@ const renderSectionHeader = ({section}) => (
 class RNTesterExampleList extends React.Component<Props, $FlowFixMeState> {
   render() {
     const filter = ({example, filterRegex}) =>
-      /* $FlowFixMe(>=0.68.0 site=react_native_fb) This comment suppresses an
-      * error found when Flow v0.68 was deployed. To see the error delete this
-      * comment and run Flow. */
       filterRegex.test(example.module.title) &&
       (!Platform.isTV || example.supportsTVOS);