allow potential_query_instability everywhere

compiler/rustc_errors/src/lib.rs

@@ -9,6 +9,7 @@
 #![feature(format_args_capture)]
 #![feature(iter_zip)]
 #![feature(nll)]
+#![cfg_attr(not(bootstrap), allow(rustc::potential_query_instability))]
 
 #[macro_use]
 extern crate rustc_macros;