Upgrade SDKs to latest version

What could be improved

• Upgrade Android SDK from 5.1.+ to 5.6.+.
• Remove the bug mention in the README.md and remove the associated file from the example

Why should this be improved

Multiple improvements on Twilio side and the bug is fixed: https://www.twilio.com/docs/video/changelog-twilio-video-android

Any risks?

No

More information

https://www.twilio.com/docs/video/changelog-twilio-video-android