Update link in documentation

The javadoc links to FontAwesome documentation have to be updated, because of a change in FontAwesome site:

+https://fontawesome.com/v6/icons/address-book?s=regular
-https://fontawesome.com/v6.0/icons/address-book

(Note that old versions are not longer documented, thus only the latest release will be available)

FontAwesomeIronIconset/src/main/generated/com/flowingcode/vaadin/addons/fontawesome/FontAwesome.java

Lines 48 to 51 in 6a9f62d

    
                   /** 
        
                    * The regular address-book icon.See <a href='https://fontawesome.com/v6.0/icons/address-book'>example</a> 
        
                    */ 
        
                   ADDRESS_BOOK,

	/**
	* The regular address-book icon.See <a href='https://fontawesome.com/v6.0/icons/address-book'>example</a>
	*/
	ADDRESS_BOOK,