ipareplica_prepare: Documentation: Fixed name of ipa_client_installed

The ipa_client_installed option was named as client_configured in the
DOCUMENTATION section.

roles/ipareplica/library/ipareplica_prepare.py

@@ -250,7 +250,7 @@ options:
     type: bool
     default: no
     required: no
-  client_configured:
+  ipa_client_installed:
     description: Was client configured already
     type: bool
     required: yes