[BUGFIX] Fix PageTree dropping behaviour

In patch #93478 (66cd4ab5) the SVG Tree Drag & Drop got a little rework.
While removing some magic strings and replacing them with enums, one
string got a wrong replacement. This caused some faulty behaviour of
the persistence of dropped pages. Changing it back to the previous
value "before" restores the old behaviour.

Resolves: #93548
Releases: master
Change-Id: I65bf14aec5540a3ae3c91dade72fad739743a5e3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70185


Tested-by: core-ci <typo3@b13.com>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Benni Mack <benni@typo3.org>