fixup: doctest - import Scanl.Prelude

Author: harendra-kumar

src/doctest/DocTestDataScanl.hs

@@ -3,5 +3,5 @@
 >>> :set -XFlexibleContexts
 >>> import Control.Concurrent (threadDelay)
 >>> import qualified Streamly.Data.Stream as Stream
->>> import qualified Streamly.Data.Scanl as Scanl
+>>> import qualified Streamly.Data.Scanl.Prelude as Scanl
 -}