[BUGFIX] Always execute pbkdf2 tests

The test annotation "@requires function hash_pbkdf2" doesn't
work for whatever reason, those tests are always skipped.
Since PHP7 always comes with hash_pbkdf2() built-in, the patch
now just drops the annotation.

Change-Id: Ice3adcebbeadf2c01e81960144c842bc4af268d2
Resolves: #76404
Releases: master
Reviewed-on: https://review.typo3.org/48422


Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>