kona-providers-alloy: drop unused HashMap import left by develop merge

Develop's #22466 removed the HashMap collect in beacon_client.rs; the
merge resolution kept this branch's import line, which all-features
clippy rejects as an unused import.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WEDeDWcHt2X1mZYhvHmnZ5

Author: claude

rust/kona/crates/providers/providers-alloy/src/beacon_client.rs

@@ -10,7 +10,7 @@ use alloy_primitives::{B256, FixedBytes};
 use async_trait::async_trait;
 use c_kzg::Blob;
 use reqwest::{self, Client};
-use std::{boxed::Box, collections::HashMap, format, string::String, sync::Arc, vec::Vec};
+use std::{boxed::Box, format, string::String, sync::Arc, vec::Vec};
 use thiserror::Error;
 
 /// The config spec engine api method.