PRVI GMM sigma

• Added vLin cap to subduction
• Removed additional squaring for crustal that was yielding small values

src/main/java/gov/usgs/earthquake/nshmp/gmm/AbrahamsonGulerce_2020.java

@@ -137,12 +137,12 @@ public abstract class AbrahamsonGulerce_2020 implements GroundMotionModel {
 
   static final double VS30_ROCK = 1000.0;
   static final double PHI_AMP_SQ = 0.09;
+  static final double VSS_MAX = 1000.0;
 
   private static final double C1S = 7.5;
   private static final double C4 = 10.0;
   private static final double C = 1.88;
   private static final double N = 1.18;
-  private static final double VSS_MAX = 1000.0;
 
   private static final double D0 = 0.47;