[TASK] Remove TYPO3_CONF_VARS[FE][allowedTempPaths]

The option "allowedTempPaths" which does this "Additional paths allowed
for temporary images.
Used with imgResource. Eg. 'alttypo3temp/,another_temp_dir/'" is not
used anymore in the core and can be removed from the core.

Resolves: #65912
Releases: master
Change-Id: Ib72abb1ac846539cc7700be824bf08a776a99b7e
Reviewed-on: http://review.typo3.org/38019


Reviewed-by: Nicole Cordes <typo3@cordes.co>
Tested-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>