0x/rm unused dep (#6899)

Co-authored-by: DaniPopes <57450786+DaniPopes@users.noreply.github.com>

crates/rpc/rpc-testing-util/src/lib.rs

@@ -5,6 +5,7 @@
     html_favicon_url = "https://avatars0.githubusercontent.com/u/97369466?s=256",
     issue_tracker_base_url = "https://github.com/paradigmxyz/reth/issues/"
 )]
+#![cfg_attr(not(test), warn(unused_crate_dependencies))]
 #![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
 
 pub mod debug;