* GenerateRealFromBits: sign is already set

If std::is_same<SignedTag, GeneratePositiveTag>::value then sign is
already set to zero thanks to:

    uint_type sign = std::is_same<SignedTag, GenerateNegativeTag>::value
                         ? (static_cast<uint_type>(1) << (kUintBits - 1))
                         : 0; // <- here

So the conditional is unnecessary.

* Update generate_real.h

Remove extra parenthesis

Co-authored-by: Derek Mauro <761129+derekmauro@users.noreply.github.com>