rust-sdk: Remove some unused imports.

src/async_client.rs

@@ -13,7 +13,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::collections::{BTreeMap, HashMap};
+#[cfg(feature = "encryption")]
+use std::collections::BTreeMap;
+use std::collections::HashMap;
 use std::convert::{TryFrom, TryInto};
 use std::result::Result as StdResult;
 use std::sync::Arc;

src/request_builder.rs

@@ -290,7 +290,7 @@ impl Into<get_message_events::Request> for MessagesRequestBuilder {
 
 #[cfg(test)]
 mod test {
-    use std::collections::{BTreeMap, HashMap};
+    use std::collections::BTreeMap;
 
     use super::*;
     use crate::events::room::power_levels::NotificationPowerLevels;