Fix scalesPageToFit property on WkWebview (it doesnt support this property)

Author: guilhermebruzzi

examples/SampleRN42/app.js

@@ -90,6 +90,7 @@ export default class Sample2 extends Component {
           onLoadStart={(event) => { console.log('webview2 onLoadStart', event.nativeEvent); }}
           onLoadEnd={(event) => { console.log('webview2 onLoadEnd', event.nativeEvent); }}
           javaScriptEnabled
+          scalesPageToFit
           source={require('./test.html')}/>
       </View>
     );

webview-bridge/index.ios.js

@@ -181,6 +181,7 @@ var WebViewBridge = React.createClass({
     let {source, ...props} = {...this.props};
     delete props.onBridgeMessage;
     delete props.onShouldStartLoadWithRequest;
+    delete props.scalesPageToFit;
 
     var webView =
       <RCTWebViewBridge