After upload, the bot do not reply with attachments with `contentUrl` set

[compulim]

In production bot, after you upload a file, the bot will say, "You have uploaded:".

Today, in production bot, it will more-or-less send us an activity looks like:

{
  attachments: [{
    contentUrl: 'https://directline.botframework.com/attachments/xxx/123.png',
    name: '123.png'
  }]
}

But, in the offline bot, it seems we are not receiving the contentUrl.

After this bug is fixed, you can look inside Web Chat code and revert it back to use offline bot. Just search some keywords in the following code.

    const { driver, pageObjects } = await setupWebDriver({
      props: {
        styleOptions: {
          enableUploadThumbnail: false
        }
      },
      // TODO: [P3] Offline bot did not reply with a downloadable attachment, we need to use production bot
      useProductionBot: true
    });