Update the pinned version of zlint from v2.2.1 to v3.1.0.
Also update the relevant path from v2 to v3 in both go.mod
and in individual imports. Update the vendored files to match.
No changes from v2.2.1 to v3.1.0 appear to affect the lints
we directly care about (e.g. those that we explicitly ignore).
Fixes#5206
Aaron Gable