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/WebApp/Configurators/IA.hs

@@ -201,7 +201,7 @@ $if (not exists)
     have been uploaded, and the Internet Archive has processed them.
 |]
   where
-  	bucket = fromMaybe "" $ M.lookup "bucket" c
+	bucket = fromMaybe "" $ M.lookup "bucket" c
 #ifdef WITH_S3
 	url = S3.iaItemUrl bucket
 #else