update typescript to 3.9.5

typings/index.d.ts

@@ -2,6 +2,5 @@ import record from './record';
 import { Replayer } from './replay';
 import { mirror } from './utils';
 export { EventType, IncrementalSource, MouseInteractions, ReplayerEvents, } from './types';
-export { pack, unpack } from './packer';
 declare const addCustomEvent: <T>(tag: string, payload: T) => void;
 export { record, addCustomEvent, Replayer, mirror };