rustc: Show `@path` usage in stable
rustc: Show `@path` usage in stable

The feature was stabilized in #66172, but the usage string was not
updated to be shown.

Signed-off-by: Miguel Ojeda <b1a5a4e53a08f19a6a1ffdf06efc0a3c0c374186@kernel.org>

graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust