[BUGFIX] Adjust table field type to varchar

In order to create workspace stage records, the parenttable field
must not be a tinytext, else the not null restriction fails on
SQlite.

Change-Id: I38cb8fca0eb293100ab7d73433cc284307eb1d0d
Resolves: #85405
Releases: master
Reviewed-on: https://review.typo3.org/58210


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>
Reviewed-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: rolandgolla <rolandgolla@gmail.com>
Tested-by: rolandgolla <rolandgolla@gmail.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>