[DOCS] Correct Changelog for ExtensionUtility::configurePlugin

The 5th parameter of ExtensionUtility::registerPlugin is thegroup and not `ExtensionUtility::PLUGIN_TYPE_CONTENT_ELEMENT`

Fixes the name to the correct function and adds example code.

Resolves: #101575
Releases: main, 12.4, 11.5
Change-Id: I05a344ee11aaa8a9b3187a11528e2e506f47756d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80354


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>