[DOCS] Fix wrong PageTypeRegistry class name in changelog

Relates: #98487
Releases: main, 12.4
Change-Id: I081e3be261d80ca59b0b170d5f9a8c3e836adae8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79009


Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Stefan Froemken <froemken@gmail.com>
Reviewed-by: Stefan Froemken <froemken@gmail.com>
Reviewed-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>