Fix wrong icon name in acp menu example

Closes #385

Author: BurntimeX

snippets/package/pip/acpMenu.xml

@@ -16,7 +16,7 @@
 			<controller>foo\acp\form\ExampleAddForm</controller>
 			<parent>foo.acp.menu.link.example.list</parent>
 			<permissions>admin.foo.canManageExample</permissions>
-			<icon>fa-plus</icon>
+			<icon>plus</icon>
 		</acpmenuitem>
 	</import>
-</data>
+</data>