Lint the typescript tests

Turns out we hadn't told eslint to lint .ts in tests/

Also fix all the lint errors, including removing a use of assert that
had randomly crept in.

test/CallHandler-test.ts

@@ -25,7 +25,6 @@ import DMRoomMap from '../src/utils/DMRoomMap';
 import EventEmitter from 'events';
 import SdkConfig from '../src/SdkConfig';
 import { ActionPayload } from '../src/dispatcher/payloads';
-import { Actions } from '../src/notifications/types';
 import { Action } from '../src/dispatcher/actions';
 
 const REAL_ROOM_ID = '$room1:example.org';