55a3d8b9 (#181) added the edition-2024 lint-level rationale to the session
bin's header naming std::env::set_var/remove_var — gate C's grep counts
comments by contract, so main went red at 5 mentions against the 4-call-site
baseline. Reword the comment instead of raising the baseline: a baseline of 5
with one comment inside would hide the next real call site.
Verified: scripts/ci/check-unsafe-hygiene.sh clean, cargo fmt clean.
enricobuehler