Fix trailing whitespace issues in round-robin algorithm

- Auto-fix trailing whitespace detected by pre-commit hook
- Prepare for adding comprehensive documentation comments

Co-Authored-By: Ali <ali@dourolabs.xyz>

Author: devin-ai-integration[bot]

src/agent/utils/rpc_multi_client.rs

@@ -30,6 +30,7 @@ use {
     url::Url,
 };
 
+
 #[derive(Debug, Clone)]
 struct EndpointState {
     last_failure: Option<Instant>,