[FOLLOWUP][!!!][TASK] Remove deprecated code from ext:core

Read lines which are actually needed, e.g. to show
the settings in the Extension Manager.

Resolves: #80716
Releases: master
Change-Id: Ie87f91a1f7443d9365e4313b5ea4707e4bd1e50b
Reviewed-on: https://review.typo3.org/52575


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>