fix some mixed space+tab indentation

This fixes all instances of " \t" in the code base. Most common case
seems to be after a "where" line; probably vim copied the two space layout
of that line.

Done as a background task while listening to episode 2 of the Type Theory
podcast.

Assistant/Threads/XMPPPusher.hs

@@ -34,7 +34,7 @@ xmppReceivePackThread = pusherThread "XMPPReceivePack" ReceivePack
 pusherThread :: String -> PushSide -> UrlRenderer -> NamedThread
 pusherThread threadname side urlrenderer = namedThread threadname $ go Nothing
   where
-  	go lastpushedto = do
+	go lastpushedto = do
 		msg <- waitPushInitiation side $ selectNextPush lastpushedto
 		debug ["started running push", logNetMessage msg]
 
@@ -78,4 +78,4 @@ selectNextPush lastpushedto l = go [] l
 		(Pushing clientid _)
 			| Just clientid /= lastpushedto -> (m, rejected ++ ms)
 		_ -> go (m:rejected) ms
-  	go [] [] = undefined
+	go [] [] = undefined