Replace std::error::Error with core::error::Error

This was stabilized in Rust 1.81 and was pointed out by the comment
above the impl.

Author: codebycruz

capstone-rs/src/error.rs

@@ -72,9 +72,7 @@ capstone_error_def!(
     => UnsupportedX86Masm = CS_ERR_X86_MASM;
 );
 
-// Required until https://github.com/rust-lang/rust/issues/103765 is resolved
-#[cfg(feature = "std")]
-impl std::error::Error for Error {}
+impl core::error::Error for Error {}
 
 pub type CsResult<T> = result::Result<T, Error>;