remove leftovers from a dropped checks

Author: ZuseZ4

compiler/rustc_codegen_llvm/messages.ftl

@@ -1,4 +1,3 @@
-codegen_llvm_autodiff_unused_args = implementation bug, failed to match all args on llvm level
 codegen_llvm_autodiff_without_enable = using the autodiff feature requires -Z autodiff=Enable
 codegen_llvm_autodiff_without_lto = using the autodiff feature requires using fat-lto
 

compiler/rustc_codegen_llvm/src/builder/autodiff.rs

@@ -10,7 +10,7 @@ use crate::back::write::llvm_err;
 use crate::builder::SBuilder;
 use crate::context::SimpleCx;
 use crate::declare::declare_simple_fn;
-use crate::errors::{AutoDiffUnusedArgs, AutoDiffWithoutEnable, LlvmError};
+use crate::errors::{AutoDiffWithoutEnable, LlvmError};
 use crate::llvm::AttributePlace::Function;
 use crate::llvm::{Metadata, True};
 use crate::value::Value;

compiler/rustc_codegen_llvm/src/errors.rs

@@ -94,10 +94,6 @@ impl<G: EmissionGuarantee> Diagnostic<'_, G> for ParseTargetMachineConfig<'_> {
 #[diag(codegen_llvm_autodiff_without_lto)]
 pub(crate) struct AutoDiffWithoutLTO;
 
-#[derive(Diagnostic)]
-#[diag(codegen_llvm_autodiff_unused_args)]
-pub(crate) struct AutoDiffUnusedArgs;
-
 #[derive(Diagnostic)]
 #[diag(codegen_llvm_autodiff_without_enable)]
 pub(crate) struct AutoDiffWithoutEnable;