[e.cash] Update instant exchanges scoring criteria

Summary: We added a new field on scorecard.cash for 'issues', and adjusted the scoring values. Updating here to reflect the same

Test Plan: Preview the site and check the instant exchanges on /get-ecash line up with those on scorecard.cash

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Subscribers: bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D14857