gui: Do not translate InitWarning messages in debug.log

Summary:

This PR forces the bitcoin-qt to write InitWarning() messages to the
debug.log file in untranslated form, i.e., in English.

Backport of core PR18922.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8647