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/SanityChecker.hs

@@ -258,7 +258,7 @@ checkOldUnused :: UrlRenderer -> Assistant ()
 checkOldUnused urlrenderer = go =<< annexExpireUnused <$> liftAnnex Annex.getGitConfig
   where
 	go (Just Nothing) = noop
-  	go (Just (Just expireunused)) = expireUnused (Just expireunused)
+	go (Just (Just expireunused)) = expireUnused (Just expireunused)
 	go Nothing = maybe noop prompt =<< describeUnusedWhenBig
 
 	prompt msg =