[clang][NFC] Remove unused parameter in `Sema::ActOnDuplicateDefinition`.

clang/include/clang/Sema/Sema.h

public:
   /// ActOnTagStartDefinition - Invoked when we have entered the
   /// scope of a tag's definition (e.g., for an enumeration, class,
   /// struct, or union).
   void ActOnTagStartDefinition(Scope *S, Decl *TagDecl);
 
   /// Perform ODR-like check for C/ObjC when merging tag types from modules.
   /// Differently from C++, actually parse the body and reject / error out
   /// in case of a structural mismatch.
-  bool ActOnDuplicateDefinition(DeclSpec &DS, Decl *Prev,
-                                SkipBodyInfo &SkipBody);
+  bool ActOnDuplicateDefinition(Decl *Prev, SkipBodyInfo &SkipBody);
 
   typedef void *SkippedDefinitionContext;
 
   /// Invoked when we enter a tag definition that we're skipping.
   SkippedDefinitionContext ActOnTagStartSkippedDefinition(Scope *S, Decl *TD);
 
   Decl *ActOnObjCContainerStartDefinition(Decl *IDecl);
 

clang/lib/Parse/ParseDecl.cpp

if (!TagDecl) {
     DS.SetTypeSpecError();
     return;
   }
 
   if (Tok.is(tok::l_brace) && TUK == Sema::TUK_Definition) {
     Decl *D = SkipBody.CheckSameAsPrevious ? SkipBody.New : TagDecl;
     ParseEnumBody(StartLoc, D);
     if (SkipBody.CheckSameAsPrevious &&
-        !Actions.ActOnDuplicateDefinition(DS, TagDecl, SkipBody)) {
+        !Actions.ActOnDuplicateDefinition(TagDecl, SkipBody)) {
       DS.SetTypeSpecError();
       return;
     }
   }
 
   if (DS.SetTypeSpecType(DeclSpec::TST_enum, StartLoc,
                          NameLoc.isValid() ? NameLoc : StartLoc,
                          PrevSpec, DiagID, TagDecl, Owned,

clang/lib/Parse/ParseDeclCXX.cpp

else if (getLangOpts().CPlusPlus)
       ParseCXXMemberSpecification(StartLoc, AttrFixitLoc, attrs, TagType,
                                   TagOrTempResult.get());
     else {
       Decl *D =
           SkipBody.CheckSameAsPrevious ? SkipBody.New : TagOrTempResult.get();
       // Parse the definition body.
       ParseStructUnionBody(StartLoc, TagType, cast<RecordDecl>(D));
       if (SkipBody.CheckSameAsPrevious &&
-          !Actions.ActOnDuplicateDefinition(DS, TagOrTempResult.get(),
-                                            SkipBody)) {
+          !Actions.ActOnDuplicateDefinition(TagOrTempResult.get(), SkipBody)) {
         DS.SetTypeSpecError();
         return;
       }
     }
   }
 
   if (!TagOrTempResult.isInvalid())
     // Delayed processing of attributes.

clang/lib/Sema/SemaDecl.cpp

void Sema::ActOnTagStartDefinition(Scope *S, Decl *TagD) {
 
   ActOnDocumentableDecl(TagD);
 
   // If there's a #pragma GCC visibility in scope, set the visibility of this
   // record.
   AddPushedVisibilityAttribute(Tag);
 }
 
-bool Sema::ActOnDuplicateDefinition(DeclSpec &DS, Decl *Prev,
-                                    SkipBodyInfo &SkipBody) {
+bool Sema::ActOnDuplicateDefinition(Decl *Prev, SkipBodyInfo &SkipBody) {
   if (!hasStructuralCompatLayout(Prev, SkipBody.New))
     return false;
 
   // Make the previous decl visible.
   makeMergedDefinitionVisible(SkipBody.Previous);
   return true;
 }