fix: reconcile canonical and security main history

What does this MR do and why?

Reconciles the diverged main branches between the canonical and security repositories so the release tooling's divergence check passes and 19.4 can be tagged.

This MR changes no files. The merge result is byte-identical to main as it stands today — it only adds history.

Background

The security repo cut v5.14.12 (4100165b) carrying the sirt_7308 ICU buffer overflow fix on 2026-09-04. The weekly release job on canonical independently cut its own v5.14.12 (4e3c0ccf) on 2026-09-08, without the fix. The fix was subsequently ported to canonical as cherry-picks (new SHAs) and shipped as v5.14.14.

The net effect: both main branches contain the same content, but they share no tip — they forked at 8d8f0aab and never rejoined. The release tooling compares refs between canonical and security and reports this as divergence, which is what is blocking the 19.4 final tag.

What this does

Merges security/main (4100165b) into canonical main so that security/main becomes an ancestor of canonical main. Once this lands, the canonical → security mirror fast-forwards and both repos agree again.

Conflicts were resolved entirely in favour of canonical's side:

File	Resolution
VERSION	5.14.14 (canonical)
CHANGELOG.md	canonical's git-cliff output, which already documents the fix under 5.14.14
third_party/icu/convert_test.go	canonical's version, including the later comment trim

The fix itself (third_party/icu/convert.go and the vendored icu module) merged cleanly — the ports are identical to the originals, so there was nothing to reconcile.

Important: merge with a merge commit

Please merge this without squash and without rebase. Either one rewrites the SHAs and security/main stops being an ancestor, which leaves the divergence in place and makes this MR pointless. The project's merge method is already set to merge, so the default is correct — just don't tick "Squash commits".

How to verify

After merging, these should agree:

git ls-remote origin refs/heads/main
git ls-remote security refs/heads/main   # after the mirror runs

Related: gitlab-org/search-team/team-tasks#296