Fix build on latest nightly

[KernelFreeze]

The feature const_in_array_repeat_expressions was removed on the latest Rust nightly, removing the feature fixes a hard compilation error on all crates that import x86_64 in nightly.

error[E0557]: feature has been removed
 --> /home/kernel/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/x86_64-0.13.1/src/lib.rs:9:43
  |
9 | #![cfg_attr(feature = "const_fn", feature(const_in_array_repeat_expressions))]
  |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ feature has been removed
  |
  = note: removed due to causing promotable bugs

error: aborting due to previous error

For more information about this error, try `rustc --explain E0557`.
error: could not compile `x86_64`

[phil-opp]

Thanks a lot!

[phil-opp]

Published as v0.13.2