[CS] Remove some uses of hasUnresolvedType in the solver

These should be unreachable now.

lib/Sema/CSBindings.cpp

@@ -115,7 +115,6 @@ static bool isGenericParameter(TypeVariableType *TypeVar) {
 bool PotentialBinding::isViableForJoin() const {
   return Kind == AllowedBindingKind::Supertypes &&
          !BindingType->hasLValueType() &&
-         !BindingType->hasUnresolvedType() &&
          !BindingType->hasTypeVariable() &&
          !BindingType->hasPlaceholder() &&
          !BindingType->hasUnboundGenericType() &&