tree-wide: Remove stray review-only assertion

Summary:
Unfortunately, these assertion don't fit the regex in the scripted-diff.
Therefore, we remove it manually

This is a backport of core#21866 [9/12]
https://github.com/bitcoin/bitcoin/pull/21866/commits/3e82abb8dd7e21ec918966105648be7ae077fd8c

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11685