[chronik] Fix the chronik_plugins test

Summary: Similar to D17680, this test expects the tx to be ordered by txid which is only true of the time first seen is the same across the txs.

Test Plan:

./test/functional/test_runner.py chronik_plugins

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17684