build(multivers-runner): hide warning due to the use of internal feat…

…ures

warning: the feature `stdarch_internal` is internal to the compiler or standard library
  |
2 | #![feature(stdarch_internal)]
  |            ^^^^^^^^^^^^^^^^
  |
  = note: using it is strongly discouraged
  = note: `#[warn(internal_features)]` on by default

multivers-runner/src/lib.rs

@@ -1,5 +1,6 @@
 #![doc = "README.md"]
 #![feature(stdarch_internal)]
+#![allow(internal_features)]
 #![cfg_attr(not(test), no_main)]
 #![cfg_attr(test, allow(dead_code))]