Remove BTreeMap from recovery.rs

src/meta/src/barrier/recovery.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
+use std::collections::{BTreeSet, HashMap, HashSet};
 use std::sync::Arc;
 use std::time::{Duration, Instant};