Remove circular toList definition.

When writing this, I assumed we have explicit `toList` as we have in
other containers. We do not have `toList`, and even if we did, the code
would not compile, as the two `toList`s (ours and `Foldable`) would
collide.

Author: foxik

Data/Sequence.hs

@@ -247,8 +247,6 @@ instance Foldable Seq where
     {-# INLINE length #-}
     null   = null
     {-# INLINE null #-}
-    toList   = toList
-    {-# INLINE toList #-}
 #endif
 
 instance Traversable Seq where