[BUGFIX] Remove obsolete `indentationPadding` property from EXT:workspaces

With #102432, the property `indentationPadding` became unused but wasn't
removed, which is now taken care of.

Resolves: #103261
Related: #102432
Releases: main
Change-Id: Ice7e63bc87c101d12e0d0e454d15b610e6469ff9
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83189


Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>
Reviewed-by: Frank Nägler <frank.naegler@typo3.com>
Tested-by: Frank Nägler <frank.naegler@typo3.com>
Tested-by: Andreas Nedbal <andy@pixelde.su>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Nedbal <andy@pixelde.su>