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/Alert.hs

@@ -145,7 +145,7 @@ syncResultAlert' succeeded failed = makeAlertFiller (not $ null succeeded) $
 		, alertHeader = Just $ tenseWords msg
 		}
   where
-  	msg
+	msg
 		| null succeeded = ["Failed to sync with", showRemotes failed]
 		| null failed = ["Synced with", showRemotes succeeded]
 		| otherwise =