Revert "Implement CIText as NOCASE alternative in postgresql"

This reverts commit 0f3c1b9d15.

core/admin/mailu/models.py

@@ -1,11 +1,10 @@
-from mailu import dkim, configuration
+from mailu import dkim
 
 from sqlalchemy.ext import declarative
 from passlib import context, hash
 from datetime import datetime, date
 from email.mime import text
 from flask import current_app as app
-from citext import CIText
 
 import flask_sqlalchemy
 import sqlalchemy
@@ -19,7 +18,6 @@ import dns
 
 
 db = flask_sqlalchemy.SQLAlchemy()
-config = configuration.ConfigManager()
 
 
 class IdnaDomain(db.TypeDecorator):
@@ -58,10 +56,6 @@ class IdnaEmail(db.TypeDecorator):
             idna.decode(domain_name),
         )
 
-    def __init__(self):
-        if config['DB_FLAVOR'] == 'postgresql':
-            self.impl = CIText()
-
 
 class CommaSeparatedList(db.TypeDecorator):
     """ Stores a list as a comma-separated string, compatible with Postfix.