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.

Backend/Hash.hs

@@ -144,7 +144,7 @@ trivialMigrate oldkey newbackend
 hashFile :: Hash -> FilePath -> Integer -> Annex String
 hashFile hash file filesize = liftIO $ go hash
   where
-  	go (SHAHash hashsize) = case shaHasher hashsize filesize of
+	go (SHAHash hashsize) = case shaHasher hashsize filesize of
 		Left sha -> sha <$> L.readFile file
 		Right command ->
 			either error return