ad-auth: Remove broken nsswitch.conf task

I don’t understand why, but it’s broken in bullseye. And this task doesn’t make sense anyway, as Debian already configures nsswitch.conf for us.

In the past, Debian configured nsswitch.conf for us---but did so over and over again. This task is in-place to prevent Debian to put sss multiple times (or too less times?) into the file (presumably over multiple ansible executions, but I don't remember the specific circumstances), which lead to erroneous behaviour. If this does not happen anymore, the task can be removed.

approved this merge request

mentioned in commit 2cddcdca

merged