[clang] [libIndex] Remove unused 'RefD' parameter of IndexingContext::handleReference()

[nridge]

Noticed this while reviewing D150124. No caller was providing a value for this parameter.

clang/lib/Index/IndexingContext.h

bool handleDecl(const Decl *D, SourceLocation Loc,
                   SymbolRoleSet Roles = SymbolRoleSet(),
                   ArrayRef<SymbolRelation> Relations = std::nullopt,
                   const DeclContext *DC = nullptr);
 
   bool handleReference(const NamedDecl *D, SourceLocation Loc,
                        const NamedDecl *Parent, const DeclContext *DC,
                        SymbolRoleSet Roles = SymbolRoleSet(),
                        ArrayRef<SymbolRelation> Relations = std::nullopt,
-                       const Expr *RefE = nullptr, const Decl *RefD = nullptr);
+                       const Expr *RefE = nullptr);
 
   void handleMacroDefined(const IdentifierInfo &Name, SourceLocation Loc,
                           const MacroInfo &MI);
 
   void handleMacroUndefined(const IdentifierInfo &Name, SourceLocation Loc,
                             const MacroInfo &MI);
 
   void handleMacroReference(const IdentifierInfo &Name, SourceLocation Loc,

clang/lib/Index/IndexingContext.cpp

return handleDeclOccurrence(D, Loc, /*IsRef=*/false, cast<Decl>(DC),
                               nullptr, OrigD, DC);
 }
 
 bool IndexingContext::handleReference(const NamedDecl *D, SourceLocation Loc,
                                       const NamedDecl *Parent,
                                       const DeclContext *DC,
                                       SymbolRoleSet Roles,
                                       ArrayRef<SymbolRelation> Relations,
-                                      const Expr *RefE,
-                                      const Decl *RefD) {
+                                      const Expr *RefE) {
   if (!shouldIndexFunctionLocalSymbols() && isFunctionLocalSymbol(D))
     return true;
 
   if (!shouldIndexTemplateParameters() &&
       (isa<NonTypeTemplateParmDecl>(D) || isa<TemplateTypeParmDecl>(D) ||
        isa<TemplateTemplateParmDecl>(D))) {
     return true;
   }
   return handleDeclOccurrence(D, Loc, /*IsRef=*/true, Parent, Roles, Relations,
-                              RefE, RefD, DC);
+                              RefE, nullptr, DC);
 }
 
 static void reportModuleReferences(const Module *Mod,
                                    ArrayRef<SourceLocation> IdLocs,
                                    const ImportDecl *ImportD,
                                    IndexDataConsumer &DataConsumer) {
   if (!Mod)
     return;