Updated javadoc to indicate which Font Awesome version is included (#14070)

Change-Id: I51c0722bda9941d16a5f6aad0ce7dfd4a4753587

server/src/com/vaadin/server/FontAwesome.java

@@ -25,6 +25,9 @@ package com.vaadin.server;
  * these icons, and all of them, so you might want to consider making a custom
  * icon font - either to get other icons, or to minimize the size of the font.
  * </p>
+ * <p>
+ * The Font Awesome version currently included is 4.0.3.
+ * </p>
  * 
  * @since 7.2
  * @author Vaadin Ltd