Revert "ENH: Set default REALM of linkahead_admin.py set_user_password to CaosDB"

This reverts commit ab95d268.

src/linkahead/utils/linkahead_admin.py

@@ -467,8 +467,8 @@ USAGE
         metavar='REALM',
         dest="realm",
         nargs="?",
-        default="CaosDB",
-        help="The realm of the user who's password is to be set.  Default is 'CaosDB'.")
+        default=None,
+        help="The realm of the user who's password is to be set.")
     subparser.add_argument(
         metavar='PASSWORD',
         nargs="?",