Sort unstable crate features list

Author: SlyMarbo

kernel/src/lib.rs

@@ -20,10 +20,10 @@
 
 #![no_std]
 #![cfg_attr(test, no_main)]
-#![feature(custom_test_frameworks)]
 #![feature(abi_x86_interrupt)]
 #![feature(alloc_error_handler)]
 #![feature(const_mut_refs)]
+#![feature(custom_test_frameworks)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]