[Chronik] Fix one coinbase height in chronik_spent_by.py test

Summary: The coinbase height is not verified in heights before 500, so this test isn't failing, but the correct height would be 102, not 101.

Test Plan: double check the height is correct

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D15511