[TASK] Disable file upload in form wizard

Due to a wrong implementation the file upload feature in the
form wizard will be disabled for the time being.

Change-Id: Ie434fade3047e8ce24fd94e5c1d4c1347024fac2
Resolves: #31274
Related: #31085
Reviewed-on: http://review.typo3.org/6320
Reviewed-by: Steffen Ritter
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert
Tested-by: Steffen Ritter
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers