Remove recently stabilized min_const_generics feature gate

    warning: the feature `min_const_generics` has been stable since 1.51.0 and no longer requires an attribute to enable
     --> tests/test.rs:3:33
      |
    3 |     feature(min_specialization, min_const_generics, type_alias_impl_trait)
      |                                 ^^^^^^^^^^^^^^^^^^
      |
      = note: `#[warn(stable_features)]` on by default

Author: dtolnay

tests/test.rs

@@ -1,6 +1,6 @@
 #![cfg_attr(
     async_trait_nightly_testing,
-    feature(min_specialization, min_const_generics, type_alias_impl_trait)
+    feature(min_specialization, type_alias_impl_trait)
 )]
 #![allow(
     clippy::let_underscore_drop,