Drop use of unstable negative_impls feature

This is no longer used anywhere.

Author: nicholasbishop

uefi-test-runner/src/main.rs

@@ -1,7 +1,6 @@
 #![no_std]
 #![no_main]
 #![feature(abi_efiapi)]
-#![feature(negative_impls)]
 
 #[macro_use]
 extern crate log;

uefi/src/lib.rs

@@ -60,7 +60,6 @@
 
 #![feature(abi_efiapi)]
 #![feature(maybe_uninit_slice)]
-#![feature(negative_impls)]
 #![feature(ptr_metadata)]
 #![cfg_attr(feature = "alloc", feature(vec_into_raw_parts))]
 #![cfg_attr(feature = "unstable", feature(error_in_core))]