[TASK] Remove saltedpasswords FE.enabled

Manually configuring clear-text password storage in TYPO3 for
frontend users by explicitly setting the ext:saltedpasswords
extension configuration "FE.enabled = 0" has been a bad idea
for a very long time already. The feature has been dropped
for backend users in core v6.2 and is now finally dropped
for frontend users with this patch, too.
No third party service must rely on clear-text password storing
in 2018 anymore, the TYPO3 authentication services provide
an API to process credentials upon user login for authentication
and authorisation purposes.

Resolves: #85027
Related: #85026
Releases: master
Change-Id: I600f598e969ac99a83f3b57362b251b48116fd58
Reviewed-on: https://review.typo3.org/56979


Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>