revert mock MatrixEvent

Author: FadhlanR

packages/host/tests/helpers/mock-matrix/_sdk.ts

@@ -1,5 +1,3 @@
-import { MatrixEvent as MatrixEventClass } from 'matrix-js-sdk';
-
 import type { ExtendedMatrixSDK } from '@cardstack/host/services/matrix-sdk-loader';
 
 import { MockClient } from './_client';
@@ -59,10 +57,4 @@ export class MockSDK implements PublicAPI<ExtendedMatrixSDK> {
     BeaconLiveness: 'RoomState.BeaconLiveness',
     Marker: 'RoomState.Marker',
   } as ExtendedMatrixSDK['RoomStateEvent'];
-
-  MatrixEvent = class MatrixEvent {
-    constructor(event: any) {
-      return new MatrixEventClass(event);
-    }
-  } as ExtendedMatrixSDK['MatrixEvent'];
 }