Death Grip should not be castable while jumping/falling and should have ...

...8-30 yards range in PvP instead of 0-30 yards
```
- float x = GetTargetUnit()->GetPositionX();
- float y = GetTargetUnit()->GetPositionY();
- float z = GetTargetUnit()->GetPositionZ();
- if (caster->GetDistance(x, y, z) < 8)

+ if(caster->GetDistance(*GetTargetUnit()) < 8.0f)
```