[ASTPrinter] Remove an unnecessary assertion

This used to be an argument to `getContextSubstitutionMap`, but that's
no longer the case. It's not important to have `CurrentModule` set
here.

Author: hamishknight

lib/AST/ASTPrinter.cpp

@@ -1159,7 +1159,6 @@ class PrintAST : public ASTVisitor<PrintAST> {
     Type OldType = CurrentType;
     if (CurrentType && (Old != nullptr || Options.PrintAsMember)) {
       if (auto *NTD = dyn_cast<NominalTypeDecl>(D)) {
-        assert(Options.CurrentModule);
         auto Subs = CurrentType->getContextSubstitutionMap(
           NTD->getDeclContext());
         setCurrentType(NTD->getDeclaredInterfaceType().subst(Subs));