Fix $FlowFixMes from TabBarIOS

Summary:
There are a number of $FlowFixMe statements in TarBarIOS.ios.js as a result of recent Flow upgrades introducing new errors/warnings. I had a stab at removing these statements and introducing what are hopefully sensible types.

Only types were changed so `yarn flow` should be sufficient.

[INTERNAL] [MINOR] [TarBarIOS] - |Fix $FlowFixMes|
Closes https://github.com/facebook/react-native/pull/16365

Differential Revision: D6200713

Pulled By: TheSavior

fbshipit-source-id: ecbd58d5831dd04250e794812ea03d202f777d12

Libraries/Components/TabBarIOS/TabBarIOS.ios.js

@@ -20,19 +20,22 @@ const ViewPropTypes = require('ViewPropTypes');
 
 var requireNativeComponent = require('requireNativeComponent');
 
-class TabBarIOS extends React.Component<{
-  style?: $FlowFixMe,
-  unselectedTintColor?: $FlowFixMe,
-  tintColor?: $FlowFixMe,
-  unselectedItemTintColor?: $FlowFixMe,
-  barTintColor?: $FlowFixMe,
+import type {StyleObj} from 'StyleSheetTypes';
+import type {ViewProps} from 'ViewPropTypes';
+
+class TabBarIOS extends React.Component<ViewProps & {
+  style?: StyleObj,
+  unselectedTintColor?: string,
+  tintColor?: string,
+  unselectedItemTintColor?: string,
+  barTintColor?: string,
   barStyle?: 'default' | 'black',
   translucent?: boolean,
   itemPositioning?: 'fill' | 'center' | 'auto',
+  children: React.Node,
 }> {
   static Item = TabBarItemIOS;
 
-  // $FlowFixMe(>=0.41.0)
   static propTypes = {
     ...ViewPropTypes,
     style: ViewPropTypes.style,
@@ -85,9 +88,7 @@ class TabBarIOS extends React.Component<{
         barStyle={this.props.barStyle}
         itemPositioning={this.props.itemPositioning}
         translucent={this.props.translucent !== false}>
-        {
-          // $FlowFixMe found when converting React.createClass to ES6
-          this.props.children}
+        {this.props.children}
       </RCTTabBar>
     );
   }