[BUGFIX] Don't render spinner when closing document

When a FormEngine document gets closed, the spinner now isn't rendered
anymore.

Resolves: #90723
Releases: master, 9.5
Change-Id: Id62c842335685a010bfbd918755b92fcd348f16c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63677


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>