setupServer: use timers module

[kentcdodds]

This is all that needs to be done to avoid issues with this code:

test('tolerates fake timers', async () => {
  server.use(
    rest.get('https://test.mswjs.io/pull', (req, res, ctx) => {
      return res(ctx.json({status: 'pulled'}))
    }),
  )
  jest.useFakeTimers()

  const res = await fetch('https://test.mswjs.io/pull')
  const body = await res.json()

  jest.useRealTimers()

  expect(body).toEqual({status: 'pulled'})
})

[kettanaito]

Happy that you've figured out the right solution to this! Thank you and welcome to contributors! 🎉