Revert "[cxx-interop] Look up NSNotificationName in C++ language mode properly"

This reverts commit e956e8a.

Author: egorzhdan

lib/ClangImporter/ClangAdapter.cpp

@@ -555,9 +555,7 @@ clang::TypedefNameDecl *importer::findSwiftNewtype(const clang::NamedDecl *decl,
     clang::LookupResult lookupResult(clangSema, notificationName,
                                      clang::SourceLocation(),
                                      clang::Sema::LookupOrdinaryName);
-    if (!clangSema.LookupQualifiedName(
-            lookupResult,
-            /*LookupCtx*/ clangSema.getASTContext().getTranslationUnitDecl()))
+    if (!clangSema.LookupName(lookupResult, clangSema.TUScope))
       return nullptr;
     auto nsDecl = lookupResult.getAsSingle<clang::TypedefNameDecl>();
     if (!nsDecl)

test/Interop/Cxx/objc-correctness/Inputs/nsnotification-bridging.h

@@ -1,4 +1,3 @@
 #import <Foundation/Foundation.h>
 
 extern NSString * const SpaceShipNotification;
-extern "C" NSString * const CExternNotification;

test/Interop/Cxx/objc-correctness/nsnotification-bridging-ide-test.swift

@@ -5,4 +5,3 @@
 // CHECK: import Foundation
 
 // CHECK: let SpaceShipNotification: String
-// CHECK: let CExternNotification: String