[Cashtab] bump extension version to support new backend per D8885

Summary: Bump extension version as this build will be submitted to chrome store

Test Plan: See Readme for extension test

Reviewers: majcosta, alcipir, Fabien, #bitcoin_abc

Reviewed By: majcosta, Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D8904