Update README

Author: kevzlou7979

README.md

@@ -17,7 +17,7 @@ AmCharts V4 Official Documentation can be found [here](https://www.amcharts.com/
 ```xml
 <dependency>
     <groupId>com.github.gwtmaterialdesign</groupId>
-    <artifactId>gwt-material-amcharts4</artifactId>
+    <artifactId>gwt-material-am4charts</artifactId>
     <version>2.2-rc1</version>
 </dependency>
 ```