[chronik] Fix check-crates

Summary: check-crates runs clippy against all the bitcoinsuite-* crates, and there is an issue with the bitcoinsuite-chronik-client.

Test Plan:

ninja check-crates

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17601