Remove unnecessary Normalization
Remove unnecessary Normalization

* In ECPubKey.TryCombine, when converting resulted Jacobian Group Element
  into GE type, it was running `Normalize()` method for each field element
  before passing to ECPubKey constructor.
  But since the constructor runs `NormalizeVariable` by itself, this operation
  is unnecessary. So this commit removes it.

MetacoSA/NBitcoin,MetacoSA/NBitcoin,NicolasDorier/NBitcoin