Move 8.2.1 withdrawal note from CHANGELOG.md to HISTORY.md

[LukasAud]

Summary

• The release-prep automation (gh changelog new) regenerates CHANGELOG.md wholesale from git tags/PRs each release. It drops the hand-written note under v9.0.0 explaining that 8.2.1 was mistakenly published as a patch (despite dropping Puppet 7 support) and was withdrawn from the Forge.
• Worse: since the v8.2.1 git tag still exists, the regenerator resurrects a ## [v8.2.1] section on the next run as if it were a normal release, with no indication it was pulled — confirmed by testing the actual release-prep workflow (see the now-closed Release prep v9.1.0 #648).
• This moves that context into HISTORY.md (which isn't touched by release-prep) as a ## 8.2.1 (Withdrawn) entry, and removes the note from CHANGELOG.md since it would be stripped by automation anyway.

Test plan

• Confirmed via the closed release-prep PR (Release prep v9.1.0 #648) that gh changelog new drops the note and reintroduces a bare v8.2.1 section.
• HISTORY.md change is additive only; CHANGELOG.md change is a two-line removal, no other content touched.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Lukas Audzevicius seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}