[BUGFIX] Ensure correct value for JsonResponse in InstallerController

Set the correct status value for the JsonResponse returned in case no
database is selected.
Additionally, a typo in the key `success` itself is fixed.

Resolves: #88066
Releases: master, 9.5
Change-Id: I3153f6cabc878b270fe48983cbdedb8ed918d566
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60466


Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Frank Naegler <frank.naegler@typo3.org>