RFR(trivial) 8213002: Remove the IgnoreUnverifiableClassesDuringDump vm option

[Calvin Cheung]

bug: https://bugs.openjdk.java.net/browse/JDK-8213002

webrev: http://cr.openjdk.java.net/~ccheung/8213002/webrev.00/

The IgnoreUnverifiableClassesDuringDump option will be obsoleted in 
JDK12. This change is for removing it in JDK13.

Testing: hs-tier{1,2} (in progress).

thanks,
Calvin