RFR: Minor cleanup of Shenandoah SA

[Aleksey Shipilev]

On 11/26/18 5:13 PM, Zhengyu Gu wrote:
> - Delete an obsoleted/commented out line.
> - Rename SHENANDOAH_HEAP to SHENANDOAH to be consistent with other GCs.
> 
> Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/minor_sa_fix/webrev.00/

Looks good.

-Aleksey