Setting browser switch in Android is not necessary and even leads to bug!

[RyanLinXiang]

Hi there,

I had a hard time to debug this:
Every time when returning to the app from PayPal or 3DSecure in Android, I would be offered a dialog 'Open with' where I can see two instances of my app. If I choose the wrong instance, the app will restart and payment would fail. I set up the browser switch as linked in the installation guide (https://developer.paypal.com/braintree/docs/guides/client-sdk/setup/android/v4#browser-switch-setup).

Now looking further into the docs from Braintree, I found out that setting browser switch in Android is obsolete => braintree/braintree_android#692

PR to update documentation: #108

Thank you!