Remove dead error code in clenv_refine_in.
Remove dead error code in clenv_refine_in.

The check for undefined metas in the conclusion could never fail. Indeed, the
dependent metas had been turned into evars before, and a meta appearing in the
conclusion is by definition dependent.

Zimmi48/coq,Zimmi48/coq,ejgallego/coq,coq/coq,SkySkimmer/coq,coq/coq,SkySkimmer/coq,SkySkimmer/coq,ejgallego/coq,SkySkimmer/coq,ejgallego/coq,ejgallego/coq,Zimmi48/coq,coq/coq,coq/coq,Zimmi48/coq