Avoid delayed bug for disabled on_type_error arguments

[TaKO8Ki]

Fixes #158628

This updates the disabled-feature path to call args.ignore_args(), matching the behavior of other diagnostic attributes.

example:

rust/compiler/rustc_attr_parsing/src/attributes/diagnostic/on_unknown.rs

Lines 13 to 21 in c397dae

	impl OnUnknownParser {
	fn parse<'sess>(&mut self, cx: &mut AcceptContext<'_, 'sess>, args: &ArgParser, mode: Mode) {
	if let Some(features) = cx.features
	&& !features.diagnostic_on_unknown()
	{
	// `UnknownDiagnosticAttribute` is emitted in rustc_resolve/macros.rs
	args.ignore_args();
	return;
	}

[rustbot]

Some changes occurred to diagnostic attributes.

cc @mejrs

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

[rustbot]

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[JonathanBrouwer]

@bors r+ rollup

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[rust-bors]

📌 Commit 673dcf0 has been approved by JonathanBrouwer

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 1. This pull request will be tested once the tree is reopened.