Bump MSRV to v1.83 (#370)

* Fix Clippy warnings for Rust v1.86

* Bump MSRV to v1.83

src/errors.rs

@@ -8,9 +8,8 @@
 
 //! A list of error types which are produced during an execution of the protocol
 use core::convert::Infallible;
+use core::error::Error;
 use core::fmt::Debug;
-#[cfg(any(feature = "std", test))]
-use std::error::Error;
 
 use displaydoc::Display;
 
@@ -85,7 +84,6 @@ impl<T: Debug> Debug for InternalError<T> {
     }
 }
 
-#[cfg(any(feature = "std", test))]
 impl<T: Error> Error for InternalError<T> {}
 
 impl InternalError {
@@ -165,7 +163,6 @@ impl<T: Debug> Debug for ProtocolError<T> {
     }
 }
 
-#[cfg(any(feature = "std", test))]
 impl<T: Error> Error for ProtocolError<T> {}
 
 // This is meant to express future(ly) non-trivial ways of converting the