Upgrade braintree_android to fix racing condition crashes

[nusjeff]

Braintree SDK Version

6.16.0

Environment

Production

Android Version & Device

Various

Braintree dependencies

implementation 'com.braintreepayments.api:drop-in:6.16.0'

Describe the bug

Our application has crashes reported on Play Console which are from Braintree SDK. This is a confirmed bug and fixed in braintree_android 4.48.0: braintree/braintree_android#982

com.braintreepayments.api:drop-in:6.16.0 still uses 4.45.0 so we should release a new version which upgrade to latest braintree_android ASAP

To reproduce

Unfortunately I'm not able to reproduce the issue as it is in some special racing conditions as explained here: braintree/braintree_android#982

Expected behavior

A new version of Dropin UI which uses latest braintree_android to avoid crashes from this racing condition

Screenshots

No response