Remove Gmail realdelete option

It can lead to potential dataloss (see recent commit log where I added a
scary warning about it to offlineimap.conf).

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/repository/Gmail.py

@@ -64,11 +64,6 @@ class GmailRepository(IMAPRepository):
     def getfoldertype(self):
         return folder.Gmail.GmailFolder
 
-    def getrealdelete(self, foldername):
-        # XXX: `foldername` is currently ignored - the `realdelete`
-        # setting is repository-wide
-        return self.getconfboolean('realdelete', 0)
-
     def gettrashfolder(self, foldername):
         #: Where deleted mail should be moved
         return  self.getconf('trashfolder','[Gmail]/Trash')