[RN] Fix regression handling ToolbarButton onPress

Introduced in
96e83989a5
as part of a refactor + feature.

react/features/toolbox/components/ToolbarButton.native.js

     _renderButton(children) {
         const props = {};
 
-        'onClick' in this.props && (props.onPress = () => {
+        'onClick' in this.props && (props.onPress = event => {
             const action = this.props.onClick(event);
 
             if (action) {