PEP 649: Fix literal block syntax (#3125)

Author: AA-Turner

pep-0649.rst

@@ -693,12 +693,10 @@ that were permitted in stock semantics, but are disallowed when
 ``from __future__ import annotations`` is active, and will have
 to be disallowed when this PEP is active:
 
-```
-:=
-yield
-yield from
-await
-```
+* ``:=``
+* ``yield``
+* ``yield from``
+* ``await``
 
 Changes to ``inspect.get_annotations`` and ``typing.get_type_hints``
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