drop the Copyable check when encountering move-only attr

this needs moer care and not required to enable the feature right now.

Author: kavon

lib/Sema/TypeCheckAttr.cpp

@@ -2159,15 +2159,6 @@ void AttributeChecker::visitFinalAttr(FinalAttr *attr) {
 }
 
 void AttributeChecker::visitMoveOnlyAttr(MoveOnlyAttr *attr) {
-#ifndef NDEBUG
-  // Try to catch uses of @_moveOnly when we don't have the Copyable protocol.
-  // This can only happen in rare circumstances with test cases where you're
-  // building with -parse-stdlib. You need to also specify that you're building
-  // the Swift module (`-module-name Swift`) and then explicitly define Copyable
-  if (!D->getASTContext().getProtocol(KnownProtocolKind::Copyable))
-    llvm_unreachable("must define Copyable protocol when using -parse-stdlib");
-#endif
-
   if (!D->getASTContext().supportsMoveOnlyTypes())
     D->diagnose(diag::moveOnly_requires_lexical_lifetimes);