Remove last vestiges of foldlStrict

The function has been gone for a while; remove comments
referring to it.

Author: treeowl

Data/Map/Internal.hs

@@ -3358,7 +3358,6 @@ fromSet f (Set.Bin sz x l r) = Bin sz x (f x) (fromSet f l) (fromSet f r)
 
 {--------------------------------------------------------------------
   Lists
-  use [foldlStrict] to reduce demand on the control-stack
 --------------------------------------------------------------------}
 #if __GLASGOW_HASKELL__ >= 708
 -- | @since 0.5.6.2

Data/Map/Strict/Internal.hs

@@ -1471,7 +1471,6 @@ fromSet f (Set.Bin sz x l r) = case f x of v -> v `seq` Bin sz x v (fromSet f l)
 
 {--------------------------------------------------------------------
   Lists
-  use [foldlStrict] to reduce demand on the control-stack
 --------------------------------------------------------------------}
 -- | /O(n*log n)/. Build a map from a list of key\/value pairs. See also 'fromAscList'.
 -- If the list contains more than one value for the same key, the last value