Fix bot-builder-webchat-overview.md

[nt-7]

Summary

This docs should be fixed as well as the following change.

[Original docs] microsoft / BotFramework-WebChat - Fix obsolete Web Chat API of Avatar #3553
microsoft/BotFramework-WebChat#3553

Description

botAvatarInitials and userAvatarInitials on How to use is obsolete API now.

There is no longer the two parameters on Web Chat API Reference.

So, it doesn't work.

Meanwhile, it works correctly if I set botAvatarInitials and userAvatarInitials on styleOptions.

Specific Changes

I remove botAvatarInitials and userAvatarInitials from Web Chat API parameters on docs.

before

window.WebChat.renderWebChat(
        {
          directLine: window.WebChat.createDirectLine({
            token: 'YOUR_DIRECT_LINE_TOKEN'
          }),
          userID: 'YOUR_USER_ID',
          username: 'Web Chat User',
          locale: 'en-US',
          botAvatarInitials: 'WC',
          userAvatarInitials: 'WW'
        },
        document.getElementById('webchat')
      );

after

window.WebChat.renderWebChat(
        {
          directLine: window.WebChat.createDirectLine({
            token: 'YOUR_DIRECT_LINE_TOKEN'
          }),
          userID: 'YOUR_USER_ID',
          username: 'Web Chat User',
          locale: 'en-US'
        },
        document.getElementById('webchat')
      );

Previously it could be set in the Web Chat API Reference, but it's obsolete now.
It is appropriate to set them in styleOptions now.

[mmiele]

The correct article will be available in the next documentation update.