[TASK] Remove ext:dbal from installation steps

We don't want to still have fresh installations that
enable ext:dbal. The patch removes the ext:dbal specific
handling from the install tool steps.
With an active loaded ext:dbal, the install tool still
works fine and runs through the steps, only new
installations can no longer choose "i do not use mysql".

Change-Id: I4b694d377df41b8ce3bd6360c7f81c9e4cd28843
Resolves: #77622
Releases: master
Reviewed-on: https://review.typo3.org/49578


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>