RFR: 8203919: Remove "-add-modules" hint from error message

[Erik Gahlin]

Hi,

Could I have a review of this fix that removes a hint when using a 
modular run-time image missing the jdk.jfr module.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8203919

Webrev:
http://cr.openjdk.java.net/~egahlin/8203919/

Thanks
Erik