Remove feature gate for stabilized feature (stabilized in 1.70.0)

[DeltaF1]

Remove feature gate for nonnull_slice_from_raw_parts

warning: the feature `nonnull_slice_from_raw_parts` has been stable since 1.70.0 and no longer requires an attribute to enable
 --> ctru-rs/src/lib.rs:7:12
  |
7 | #![feature(nonnull_slice_from_raw_parts)]
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(stable_features)]` on by default

[DeltaF1]

Ah I see now that the project targets a specific older nightly version as well. Good to know.

[Meziu]

Yeah it’s a bit annoying when using the newer toolchains, but it’s fine. We will update the minimum version once a good chunk of the unstable features we use get stabilised.