Fixes docs of Data.HashMap.Lazy.fromList: it takes O(n * log(n)) (#498)

Fixes the incorrect documentation in Data.HashMap.Lazy.fromList
/ Data.HashMap.Internal.fromList: This takes linearithmic time
rather than linear time, since we do n insertions, each of which
takes (assuming no collisions!) log32(n) steps as per the documentation
of insert.

Fixes #309

Author: Qqwy

Data/HashMap/Internal.hs

@@ -2233,7 +2233,7 @@ toList :: HashMap k v -> [(k, v)]
 toList t = Exts.build (\ c z -> foldrWithKey (curry c) z t)
 {-# INLINE toList #-}
 
--- | \(O(n)\) Construct a map with the supplied mappings.  If the list
+-- | \(O(n \log n)\) Construct a map with the supplied mappings.  If the list
 -- contains duplicate mappings, the later mappings take precedence.
 fromList :: (Eq k, Hashable k) => [(k, v)] -> HashMap k v
 fromList = List.foldl' (\ m (k, v) -> unsafeInsert k v m) empty