[DOCS] Use correct data type for DependencyOrdering

As the new additional file processors registration
also uses the DependencyOrderingService the value
of `before` must be an array instead of a string.

Releases: master
Resolves: #89931
Change-Id: I8eea65c56f68ae94cddb239ac9e08c18a59ee036
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62610


Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: Alexander Schnitzler <review.typo3.org@alexanderschnitzler.de>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Alexander Schnitzler <review.typo3.org@alexanderschnitzler.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>