Remove unneeded imports of UIBase

Code was broken, as these backends import UIBase (which had been moved).
However, they don't use it, so we can just delete the import.
Sorry, I failed to find those earlier somehow.

Signed-off-by: Sebastian <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/folder/Gmail.py

@@ -22,7 +22,6 @@
 from IMAP import IMAPFolder
 import imaplib
 from offlineimap import imaputil, imaplibutil
-from offlineimap.ui import UIBase
 from copy import copy
 
 

offlineimap/folder/UIDMaps.py

@@ -19,7 +19,6 @@
 from threading import *
 from offlineimap import threadutil
 from offlineimap.threadutil import InstanceLimitedThread
-from offlineimap.ui import UIBase
 from IMAP import IMAPFolder
 import os.path, re