Remove FIXMEs referencing #44232

[theemathas]

#44232 is already closed, since #152164 implemented the unused_features lint.

The deleted tests, as currently written, make no sense. Relevant functionality is already tested in:

• tests/ui/feature-gates/unknown-feature.rs
• tests/ui/feature-gates/stable-features.rs
• tests/ui/lint/unused-features/unused-language-features.rs

[rustbot]

r? @petrochenkov

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[riking]

lint-unknown-feature has sure gone on an Incredible Journey. When originally added in a9bd049, the test read as follows:

// Copyright 2013 The Rust Project Developers.
// ... copyright header continues ...

#[deny(unknown_features)];

#[feature(this_is_not_a_feature)]; //~ ERROR: unknown feature

fn main() {}

And today it is:

//@ check-pass

#![warn(unused_features)]

#![allow(stable_features)]
// FIXME(#44232) we should warn that this isn't used.

fn main() {}

[petrochenkov]

@bors r+ rollup

[rust-bors]

📌 Commit 4b1bfb5 has been approved by petrochenkov

It is now in the queue for this repository.