remove specification feature

Signed-off-by: iosmanthus <[email protected]>

Author: iosmanthus

src/lib.rs

@@ -92,7 +92,6 @@
 //! # })}
 //! ```
 
-#![feature(min_specialization)]
 #![feature(explicit_generic_args_with_impl_trait)]
 #[macro_use]
 pub mod request;