Remove unused focusedOpacity prop and function

Summary:
The `focusedOpacity` prop is only used inside `_opacityFocused` which is not used anywhere. This pr removes this unused code.
The code was added in https://github.com/facebook/react-native/pull/10427 but it does not appear to be used in the final version of the pr.
Closes https://github.com/facebook/react-native/pull/14984

Differential Revision: D5430611

Pulled By: shergin

fbshipit-source-id: 0bc4fdef04304eae9785caaf76ae1fb12ce6651e

Libraries/Components/Touchable/TouchableOpacity.js

@@ -63,7 +63,6 @@ var TouchableOpacity = createReactClass({
      * active. Defaults to 0.2.
      */
     activeOpacity: PropTypes.number,
-    focusedOpacity: PropTypes.number,
     /**
      * Apple TV parallax effects
      */
@@ -73,7 +72,6 @@ var TouchableOpacity = createReactClass({
   getDefaultProps: function() {
     return {
       activeOpacity: 0.2,
-      focusedOpacity: 0.7,
     };
   },
 
@@ -165,10 +163,6 @@ var TouchableOpacity = createReactClass({
     );
   },
 
-  _opacityFocused: function() {
-    this.setOpacityTo(this.props.focusedOpacity);
-  },
-
   _getChildStyleOpacityWithDefault: function() {
    var childStyle = flattenStyle(this.props.style) || {};
    return childStyle.opacity == undefined ? 1 : childStyle.opacity;