library/ipatest.py: Drop unused prinipal from module parameters

The principal is not used and needed in the module, therefore it got removed.

roles/ipaclient/tasks/install.yml

@@ -35,7 +35,6 @@
       realm: "{{ ipadiscovery.realm }}"
       hostname: "{{ ipadiscovery.hostname }}"
       kdc: "{{ ipadiscovery.kdc }}"
-      principal: "{{ ipaadmin_principal if not ipaclient_use_otp | bool else '' }}"
       kinit_attempts: "{{ ipaclient_kinit_attempts | default(omit) }}"
     register: ipatest