Bump version to 15.10.2

This releases the airgapped probe change (!1477 (merged)), which merged after 15.10.1 was tagged. gitlab-org/gitlab pins gitlab-qa 15.10.1 (qa/Gemfile.lock:146), so its airgapped job still runs the old probes, including a post-rules wget check that exits 0 whatever the fetch does. The job runs the new probes once gitlab-org/gitlab takes 15.10.2.

15.10.2 is a patch bump:

• The release notes list one change, !1477 (merged). It fixes a check that could not fail and adds two log lines (whether gitlab.com port 8080 is reachable, and how many packets the OUTPUT policy dropped) that never fail the job.
• It changes the airgapped scenario (airgapped.rb), adds its spec and a short passage to docs/what_tests_can_be_run.md. No scenario or CLI option is added, removed or renamed. Earlier patch releases carried additions of this kind, such as 14.19.2 (a passed-through CI variable) and 15.7.1 (pre-release version detection).
• After the bump, the airgapped job in gitlab-org/gitlab also fails when gitlab.com port 443, example.com port 80 or 443, or dns.google port 53 is reachable once the rules are in. Before the rules go in, it needs example.com port 443 reachable and example.com and dns.google resolvable.

An AI coding assistant wrote this change and ran the specs and RuboCop on it.

Diff

15.10.1...e98305d1

Pre-merge checklist

• Diff link is up-to-date.
• Check the release notes: https://gitlab.com/api/v4/projects/gitlab-org%2Fgitlab-qa/repository/changelog?version=15.10.2
• Based on the diff and the release notes, version.rb is updated, according to SemVer.

Post-merge checklist

• In the pipeline-common project, update the GITLAB_QA_VERSION (make sure to add a Changelog: trailer to the commit) and create a release.
• Unless already done by renovate-gitlab-bot, in the GitLab project, update the ref for pipeline-common in .gitlab/ci/qa-common/main.gitlab-ci.yml.
• Unless already done by renovate-gitlab-bot, or if you need it sooner, in the GitLab project, update the gitlab-qa gem version in qa/Gemfile and qa/Gemfile.lock (for an example, see: gitlab!117054 (merged)).