PEP 663: Fix markup

Author: gvanrossum

pep-0663.txt

@@ -63,7 +63,7 @@ str() output of each should be its inherent value; e.g. if ``Color`` is an
 Note that format() already produces the correct output in 3.10, only str() needs
 updating.
 
-As much as possible, the ``str()`, ``repr()``, and ``format()`` of enum members
+As much as possible, the ``str()``, ``repr()``, and ``format()`` of enum members
 should be standardized across the standard library.
 
 The repr() of Flag currently includes aliases, which it should not; fixing that