Fix a bug in serialization of witness methods

Author: swiftix

lib/SILGen/SILGenType.cpp

@@ -477,10 +477,7 @@ class SILGenConformance : public SILGenWitnessTable<SILGenConformance> {
     if (witnessSerialized &&
         fixmeWitnessHasLinkageThatNeedsToBePublic(witnessLinkage)) {
       witnessLinkage = SILLinkage::Public;
-      witnessSerialized =
-          (SGM.M.getASTContext().LangOpts.SILSerializeWitnessTables
-               ? IsSerialized
-               : IsNotSerialized);
+      witnessSerialized = IsNotSerialized;
     } else {
       // This is the "real" rule; the above case should go away once we
       // figure out what's going on.