[e.cash] Filter out low exchange scores

Summary:
As discussed adding some logic to scores.js to filter out scores below a certain threshold (60 for now)
Updated the test data to reflect this and modified a test so it would pass

Test Plan:
Preview the site and check items on the get-ecash page with low scores are gone
check all test pass - npm run test

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien, Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D14707