[Sema] Fix -Wunused-but-set-variable after #94865

Author: MaskRay

clang/lib/Sema/SemaLambda.cpp

@@ -1246,7 +1246,7 @@ void Sema::ActOnLambdaExpressionAfterIntroducer(LambdaIntroducer &Intro,
 
       if (auto *BD = R.getAsSingle<BindingDecl>())
         Var = BD;
-      else if (auto *FD = R.getAsSingle<FieldDecl>()) {
+      else if (R.getAsSingle<FieldDecl>()) {
         Diag(C->Loc, diag::err_capture_class_member_does_not_name_variable)
             << C->Id;
         continue;