Remove empty decryption listener (#2486)

* Remove empty decryption listener

This listener looks like it was left over from something as it just
did nothing at all. The todevice event gets put into the call
event buffer which awaits on decryption for each event before
processing, so it should already wait for decryption.

More info: element-hq/element-call#428

* Unused import

* Unused function!

src/webrtc/callEventHandler.ts

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { MatrixEvent, MatrixEventEvent } from '../models/event';
+import { MatrixEvent } from '../models/event';
 import { logger } from '../logger';
 import { CallDirection, CallErrorCode, CallState, createNewMatrixCall, MatrixCall } from './call';
 import { EventType } from '../@types/event';
@@ -140,13 +140,6 @@ export class CallEventHandler {
             this.nextSeqByCall.set(content.call_id, 0);
         }
 
-        if (event.isBeingDecrypted() || event.isDecryptionFailure()) {
-            // add an event listener for once the event is decrypted.
-            event.once(MatrixEventEvent.Decrypted, async () => {
-                if (!this.eventIsACall(event)) return;
-            });
-        }
-
         if (content.seq === undefined) {
             this.callEventBuffer.push(event);
             return;
@@ -184,15 +177,6 @@ export class CallEventHandler {
         }
     };
 
-    private eventIsACall(event: MatrixEvent): boolean {
-        const type = event.getType();
-        /**
-         * Unstable prefixes:
-         *   - org.matrix.call. : MSC3086 https://github.com/matrix-org/matrix-doc/pull/3086
-         */
-        return type.startsWith("m.call.") || type.startsWith("org.matrix.call.");
-    }
-
     private async handleCallEvent(event: MatrixEvent) {
         this.client.emit(ClientEvent.ReceivedVoipEvent, event);