[BUGFIX] Remove save and new button for sys_file

The save and new button does not make any sense for file
meta data, so we should not display it.

Resolves: #45044
Releases: 6.0, 6.1

Change-Id: Ic25edee5b208103f74c7d566acb93099bdd3c19f
Reviewed-on: https://review.typo3.org/17898
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel