Fix syntax error

pep-0422.txt

@@ -295,6 +295,8 @@ custom metaclasses and even ``__new__`` methods can already do this
 implicitly, but the decorator model makes such code much easier to understand
 and implement.
 
+::
+
    class BuildDict:
        def __autodecorate__(cls):
            cls = super().__autodecorate__()
@@ -564,4 +566,3 @@ This document has been placed in the public domain.
    fill-column: 70
    coding: utf-8
    End:
-