[lint] fix a false positive locale dependence detection

Summary: Introduced by D16209 because I didn't include arc lint --everything in the test plan.

Test Plan:
arc lint --everything

Check that there are no more errors related to cpp files.
I'm still getting some warnings and autofixes for .rs, .ts, .md and .js files, but that could be because I'm not using the right versions of prettier and rustfmt

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16330