[clang][modules] Don't hard code [no_undeclared_includes] for the Darwin module

The Darwin module has specified [no_undeclared_includes] for at least five years now, there's no need to hard code it in the compiler.

Reviewed By: ributzka, Bigcheese

Differential Revision: https://reviews.llvm.org/D132971

Author: ian-twilightcoder

clang/lib/Lex/ModuleMap.cpp

@@ -2026,8 +2026,7 @@ void ModuleMapParser::parseModuleDecl() {
     ActiveModule->IsSystem = true;
   if (Attrs.IsExternC)
     ActiveModule->IsExternC = true;
-  if (Attrs.NoUndeclaredIncludes ||
-      (!ActiveModule->Parent && ModuleName == "Darwin"))
+  if (Attrs.NoUndeclaredIncludes)
     ActiveModule->NoUndeclaredIncludes = true;
   ActiveModule->Directory = Directory;