scrypt can be doctested now that we're using 1.1.0 (#3688)

diff --git a/docs/hazmat/primitives/key-derivation-functions.rst b/docs/hazmat/primitives/key-derivation-functions.rst
index d419b85..6195880 100644
--- a/docs/hazmat/primitives/key-derivation-functions.rst
+++ b/docs/hazmat/primitives/key-derivation-functions.rst
@@ -753,7 +753,7 @@
     :class:`~cryptography.hazmat.primitives.kdf.KeyDerivationFunction`
     interface.
 
-    .. code-block:: python
+    .. doctest::
 
         >>> import os
         >>> from cryptography.hazmat.primitives.kdf.scrypt import Scrypt