[BUGFIX] Do not check HTTP referrer anymore

Under certain circumstances some browsers do not set the HTTP referrer
anymore due to privacy reasons. Hence, checking the referrer breaks
functionality.

The configuration option [SYS][doNotCheckReferer] is also removed as
it is not needed anymore.

Resolves: #83768
Releases: master, 8.7, 7.6
Change-Id: Ia8f882e07a9e2091ceb38aee814badb97403250d
Reviewed-on: https://review.typo3.org/55556


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>