[embedded] Use the type witness from the specialized conformance

rather then the specialized conformance's root conformance (which is the  variable's value)

Author: aschwaighofer

lib/IRGen/GenProto.cpp

@@ -1750,11 +1750,11 @@ class AccessorConformanceInfo : public ConformanceInfo {
       (void)entry;
 #endif
 
-      auto typeWitness = Conformance.getTypeWitness(assocType);
-      if (langOpts.hasFeature(Feature::EmbeddedExistentials) &&
-          SILWT->isSpecialized()) {
+      Type typeWitness;
+      if (SILWT->isSpecialized())
         typeWitness = entry.getAssociatedTypeWitness().Witness;
-      }
+      else
+        typeWitness = Conformance.getTypeWitness(assocType);
 
       if (IGM.Context.LangOpts.hasFeature(Feature::EmbeddedExistentials)) {
         // In Embedded Swift associated type witness point to the metadata.