AST: Remove check for '@objc' protocols when computing nested types

This fixes a crash with malformed code with the next patch.

Author: slavapestov

lib/AST/Type.cpp

@@ -2720,9 +2720,6 @@ void ArchetypeType::populateNestedTypes() const {
   llvm::SmallPtrSet<Identifier, 4> knownNestedTypes;
   ProtocolType::visitAllProtocols(getConformsTo(),
                                   [&](ProtocolDecl *proto) -> bool {
-    // Objective-C protocols don't have type members.
-    if (proto->isObjC()) return false;
-
     for (auto member : proto->getMembers()) {
       if (auto assocType = dyn_cast<AssociatedTypeDecl>(member)) {
         if (knownNestedTypes.insert(assocType->getName()).second)