[DOCS] Use correct ReST file syntax in changelog

Some changelog files containing invalid Sphinx syntax,
thus adding warnings during documentation build.

This change adjusts some changelog files to avoid
these warnings.

* use correct link target syntax
* ensure correct usage of code blocks

Resolves: #99099
Releases: main
Change-Id: Ib883ed6cb94bad98f5eb0d893d008728a3e1dc2d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76636


Tested-by: core-ci <typo3@b13.com>
Tested-by: Chris Müller <typo3@krue.ml>
Reviewed-by: Chris Müller <typo3@krue.ml>
Tested-by: Lina Wolf <112@linawolf.de>
Reviewed-by: Lina Wolf <112@linawolf.de>