Remove unused code

Author: tesaguri

oauth1-request-derive/src/lib.rs

@@ -16,9 +16,6 @@
 
 #![doc(html_root_url = "https://docs.rs/oauth1-request-derive/0.4.1")]
 
-#[allow(unused_extern_crates)]
-extern crate proc_macro;
-
 mod field;
 mod method_body;
 mod util;