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.

ad-auth/tasks/sssd.yml

@@ -98,16 +98,6 @@
   tags:
     - sssd
 
-# taken out of Debian's post install hooks
-- name: ensure sssd is configured in nsswitch.conf  # noqa 301 306
-  # yamllint disable-line rule:line-length
-  shell: "sed -i --regexp-extended '/^(passwd|group|shadow|netgroup|services):/ {
-  /\\bsss\\b/! s/$/ sss/  } ' /etc/nsswitch.conf"
-  args:
-    warn: false
-  tags:
-    - sssd
-
 - name: ensure sssd is enabled and running
   service:
     name: sssd