[!!!][TASK] Remove leftover deprecated hooks

Due to testing framework refactoring, the 2 leftover hooks
in Frontend middlewares can now be removed:

$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['tslib/class.tslib_fe.php']['initFEuser']
$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['tslib/index_ts.php']['postBeUser']

Thus, Frontend Middleware stack is now free of hooks.

Resolves: #87357
Releases: master
Change-Id: I076d9f4aa556f4ba111196449eee6449ba8036db
Reviewed-on: https://review.typo3.org/59364
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>