Replace BTreeSet with HashSet

common-api/src/api.rs

 use crate::crypto::prelude::*;
 use near_account_id::AccountId;
 use serde::{Deserialize, Serialize};
-use std::{collections::BTreeSet, time::Duration};
+use std::{collections::HashSet, time::Duration};
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct PublicKeys {
     pub timeout: Duration,
-    pub participants: BTreeSet<AccountId>,
+    pub participants: HashSet<AccountId>,
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize)]