Remove useless additionnal blur call (#22156)

Summary:
I noticed that the _onBlur method was not exactly similar to the _onFocus one in the TextInput component.

After digging, I found that the blurTextInput method in the TextInputState.js file was call twice in a raw instead of once when the textinput component should blur.

By removing this line, I fix this unecessary multiple call.
Pull Request resolved: https://github.com/facebook/react-native/pull/22156

Reviewed By: TheSavior

Differential Revision: D13105396

Pulled By: RSNara

fbshipit-source-id: 8e83461d8b288d8ee4047bc4a33c4480e193c349

Libraries/Components/TextInput/TextInput.js

@@ -1202,7 +1202,6 @@ const TextInput = createReactClass({
   },
 
   _onBlur: function(event: Event) {
-    this.blur();
     if (this.props.onBlur) {
       this.props.onBlur(event);
     }