Fix markup

Thanks, @hynek!
diff --git a/doc/api/crypto.rst b/doc/api/crypto.rst
index cfcc058..101f3bd 100644
--- a/doc/api/crypto.rst
+++ b/doc/api/crypto.rst
@@ -340,6 +340,6 @@
 :py:class:`CRL`            :py:class:`CRLType`
 =========================  =============================
 
-Some objects, such as py:class`Revoked`, don't have ``Type``
+Some objects, such as :py:class`Revoked`, don't have ``Type``
 equivalents, because they were added after the restriction had been
 lifted.