#[lang] not feature gated

### Summary

See title

### Reproducer

I tried this code:

```rust
#[lang = "sized"]
trait Sized {}
```


### Does the code make use of any (1.49) nightly feature ?

- [ ] Nightly

### Godbolt link

_No response_

### Actual behavior

It compiles

### Expected behavior

It should require `#![feature(lang_items)]`

### GCC Version

gccrs (Compiler-Explorer-Build-gcc--binutils-2.44) 15.2.0