[TASK] Remove two unused settings from LocalConfiguration

The two (internal) settings 'SYS/isInitialInstallationInProgress' and
'SYS/isInitialDatabaseImportDone' have been obsoleted with
the install tool rewrite in v9 and can be removed from
LocalConfiguration using the SilentConfigurationUpgradeService.

Change-Id: I6c80506f2389004093f43ff9fc3df49b002e1438
Resolves: #83878
Releases: master
Reviewed-on: https://review.typo3.org/55696


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>