Remove local hack

Author: DougGregor

lib/AST/ProtocolConformance.cpp

@@ -720,13 +720,11 @@ void NormalProtocolConformance::setWitness(ValueDecl *requirement,
   assert(getProtocol() == cast<ProtocolDecl>(requirement->getDeclContext()) &&
          "requirement in wrong protocol");
   assert(Mapping.count(requirement) == 0 && "Witness already known");
-#if false
   assert((!isComplete() || isInvalid() ||
           requirement->getAttrs().hasAttribute<OptionalAttr>() ||
           requirement->getAttrs().isUnavailable(
                                         requirement->getASTContext())) &&
          "Conformance already complete?");
-#endif
   Mapping[requirement] = witness;
 }