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/Pairing.hs

@@ -72,7 +72,7 @@ getStartXMPPPairSelfR :: Handler Html
 #ifdef WITH_XMPP
 getStartXMPPPairSelfR = go =<< liftAnnex getXMPPCreds
   where
-  	go Nothing = do
+	go Nothing = do
 		-- go get XMPP configured, then come back
 		redirect XMPPConfigForPairSelfR
 	go (Just creds) = do