adding missing props to save func in es5 example (#13752)

In the ES5 example for the RichText component the props are not passed into the save function. Inside the save function they are called though.

packages/editor/src/components/rich-text/README.md

@@ -83,7 +83,7 @@ wp.blocks.registerBlockType( /* ... */, {
 		} );
 	},
 
-	save: function() {
+	save: function( props ) {
 		return wp.element.createElement( wp.editor.RichText.Content, {
 			tagName: 'h2', value: props.attributes.content
 		} );