[!!!][TASK] Remove BE/fileExtensions/webspace

The option $TYPO3_CONF_VARS[BE][fileExtensions][webspace][*]
is removed.

It was only used in some specific cases, whereas fileDenyPattern usage
is more consistently done and replaces this setting.

Resolves: #83081
Releases: master
Change-Id: I1327ad000c08d8619366c03838b01261f91fa945
Reviewed-on: https://review.typo3.org/54634


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>