[Sema] Remove an unnecessary cast (NFC) (#147546)

D is already of CXXMethodDecl *.

Author: kazutakahirata

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -3029,7 +3029,7 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
   LocalInstantiationScope Scope(SemaRef, MergeWithParentScope);
 
   Sema::LambdaScopeForCallOperatorInstantiationRAII LambdaScope(
-      SemaRef, const_cast<CXXMethodDecl *>(D), TemplateArgs, Scope);
+      SemaRef, D, TemplateArgs, Scope);
 
   // Instantiate enclosing template arguments for friends.
   SmallVector<TemplateParameterList *, 4> TempParamLists;