Remove unused sound callback

src/components/target-pane/target-pane.jsx

@@ -162,7 +162,6 @@ TargetPane.propTypes = {
     onChangeSpriteY: React.PropTypes.func,
     onDeleteSprite: React.PropTypes.func,
     onNewBackdropClick: React.PropTypes.func,
-    onNewSoundClick: React.PropTypes.func,
     onNewSpriteClick: React.PropTypes.func,
     onRequestCloseBackdropLibrary: React.PropTypes.func,
     onRequestCloseCostumeLibrary: React.PropTypes.func,

src/containers/target-pane.jsx

@@ -5,7 +5,6 @@ const {connect} = require('react-redux');
 
 const {
     openBackdropLibrary,
-    openSoundLibrary,
     openSpriteLibrary,
     closeBackdropLibrary,
     closeCostumeLibrary,
@@ -99,10 +98,6 @@ const mapDispatchToProps = dispatch => ({
         e.preventDefault();
         dispatch(openBackdropLibrary());
     },
-    onNewSoundClick: e => {
-        e.preventDefault();
-        dispatch(openSoundLibrary());
-    },
     onNewSpriteClick: e => {
         e.preventDefault();
         dispatch(openSpriteLibrary());