s/consts/const items/

Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>

Author: Aaron1011

src/test/run-pass/existential_type_const.rs

@@ -2,7 +2,7 @@
 #![feature(impl_trait_in_bindings)]
 //~^ WARN the feature `impl_trait_in_bindings` is incomplete and may cause the compiler to crash
 
-// Ensures that consts can constrain an existential type
+// Ensures that `const` items can constrain an `existential type`.
 
 use std::fmt::Debug;