[trivial] turn test runner cli output into Bitcoin Cash

Summary:
this change borrows a Ghanaian Cedi symbol (₵) and appends it to the
existing ₿ in the test_runner.py output, for a more ₿₵ feel.

Test Plan:

./test/functional/test_runner.py

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5976