[TASK] DatabaseRecordList: Drop property `showIcon`

The property `showIcon` was always  1. Therefore, it has been removed.

Releases: master
Resolves: #92211
Change-Id: I852bc2c007f77522b3b80423f92f28a5be3c22b5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65591


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Jörg Bösche <typo3@joergboesche.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>