Faster computation of relevance_of_term for Prod.
Faster computation of relevance_of_term for Prod.

The previous code was computing it based on the codomain. While technically
equivalent for well-typed terms, this is useless since we know that Prod has
a type which is always a sort, and therefore is always relevant as a term.

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