fix(Presence): ensure player collider height is set correctly

A recent update to how the collider height was calculated to ensure
a scaled CameraRig would still work, ended up breaking the normal
usage of the collider.

This fix ensures the collider height works correctly at normal scale
and if the CameraRig is scaled.

Assets/VRTK/Scripts/VRTK_PlayerPresence.cs

@@ -297,7 +297,7 @@ private void DisablePhysics()
         private void UpdateCollider()
         {
             var playAreaHeightAdjustment = 0.009f;
-            var newpresenceColliderYSize = (headset.transform.localPosition.y - headsetYOffset) - transform.localPosition.y;
+            var newpresenceColliderYSize = (headset.transform.localPosition.y - headsetYOffset);
             var newpresenceColliderYCenter = (newpresenceColliderYSize != 0 ? (newpresenceColliderYSize / 2) + playAreaHeightAdjustment : 0);
 
             if (presenceCollider)