[BUGFIX] Cast id to integer in class BackendUserConfigurationUpdate

The newly introduced BackendUserConfigurationUpdate tries to pass a
string value id to the updateBackendUser() function, which requires an
integer. This commit solves that problem

Resolves: #89683
Releases: master, 9.5
Change-Id: Ieca98c01ec44b7e3a4275d645fa6d25ea09d63a2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62350


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>