[SECURITY] Remove TYPO3 version from installer

When installing TYPO3, the current version
is shown without any kind of authentication
provided (no FIRST_INSTALL). This information
disclosure is solved.

Resolves: #86254
Releases: master, 8.7, 7.6
Security-Commit: a69d09ab4eabd0474f0191f5daf525d91ebaa32f
Security-Bulletin: TYPO3-CORE-SA-2018-010
Change-Id: Ib8359937716dce4839d76b054b0d0d549bd4aa0c
Reviewed-on: https://review.typo3.org/59104


Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>