message: chore(exhaust-spec): replace cold with hot observable
  Thanks.
diff: @@ -14,14 +14,22 @@ describe('exhaust', () => {
  });
  it('should handle a hot observable of hot observables', () => {
  - testScheduler.run(({ cold, hot, expectObservable }) => {
  - const x = cold(' --a---b---c--| ');
  - const y = cold(' ---d--e---f---| ');
  - const z = cold(' ---g--h---i---|');
  + testScheduler.run(({ hot, expectObservable, expectSubscriptions }) => {
  + const x = hot(' -----a---b---c--| ');
  + const xsubs = ' ------^---------! ';
  + const y = hot(' -------d--e---f---| ');
  + const ysubs: string[] = [];
  + const z = hot(' --------------g--h---i---| ');
  + const zsubs = ' --------------------^----! ';
  const e1 = hot(' ------x-------y-----z-------------|', { x: x, y: y, z: z });
  - const expected = '--------a---b---c------g--h---i---|';
  + const e1subs = ' ^---------------------------------!';
  + const expected = '---------b---c-------i------------|';
  expectObservable(e1.pipe(exhaust())).toBe(expected);
  + expectSubscriptions(e1.subscriptions).toBe(e1subs);
  + expectSubscriptions(x.subscriptions).toBe(xsubs);
  + expectSubscriptions(y.subscriptions).toBe(ysubs);
  + expectSubscriptions(z.subscriptions).toBe(zsubs);
  });
  });
  