[TASK] Avoid request dependent data in scheduler test task

Accessing request dependent data in a scheduler
task is problematic on CLI. For this reason tasks
have no setRequest() method or similar.

The task does not loose much information avoiding
a GU::getIndpEnv() for the test mail, and the
setRequest() on the mail object is unused.

Change-Id: I87a74c1d48eaa894c2859b235886ed57300c8a8b
Resolves: #94748
Related: #94632
Releases: master
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70289


Tested-by: core-ci <typo3@b13.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Benni Mack <benni@typo3.org>