Remove TextInput's inputView prop

Summary:
This if statement is older than June 2015. This prop is undocumented, not part of the flow type, not on our public docs, not in the flow type, not in typescript types, and I can't find any blog posts about it.

Changelog:
[Breaking][TextInput] Removing undocumented `inputView` prop. Use children instead.

Reviewed By: yungsters

Differential Revision: D18296894

fbshipit-source-id: 95373d24659e6f06e212095b57e8f6d713323c11

Author: elicwhite

Libraries/Components/TextInput/TextInput.js

@@ -948,9 +948,6 @@ const TextInput = createReactClass({
           </Text>
         );
       }
-      if (props.inputView) {
-        children = [children, props.inputView];
-      }
       props.style.unshift(styles.multilineInput);
       textContainer = (
         <RCTMultilineTextInputView