[ecash-lib] Bump integration-tests timeout

Summary: Sometimes the before step when setting up the regtest takes longer than 2000ms, so we bump it to 60000ms.

Test Plan: npm run integration-tests

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D16046