RFR: 8229128: ZGC: Remove unused ZThreadRootsIterator

[Stefan Karlsson]

Looks good.

StefanK

On 2019-08-05 13:37, Per Liden wrote:
> ZThreadRootsIterator is no longer used and can be removed. Trivial?
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8229128
> Webrev: http://cr.openjdk.java.net/~pliden/8229128/webrev.0
> 
> /Per