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/Utility.hs

@@ -119,7 +119,7 @@ mergeAlert i al m = maybe updatePrune updateCombine (alertCombiner al)
 	  where
 		bloat = M.size m' - maxAlerts
 		pruneold l =
-	 		let (f, rest) = partition (\(_, a) -> isFiller a) l
+			let (f, rest) = partition (\(_, a) -> isFiller a) l
 			in drop bloat f ++ rest
 	updatePrune = pruneBloat $ M.filterWithKey pruneSame $
 		M.insertWith' const i al m