Issue #12947: Remove doctest directives from the doctest examples in the "Option Flag" section.

The doctest examples that illustrate the use of doctest option flags
independent of doctest directives should not display doctest directives.

Doc/library/doctest.rst

@@ -552,11 +552,11 @@ doctest decides whether actual output matches an example's expected output:
    both of these variations will work with the flag specified, regardless of
    whether the test is run under Python 2.7 or Python 3.2 (or later versions)::
 
-      >>> raise CustomError('message') #doctest: +IGNORE_EXCEPTION_DETAIL
+      >>> raise CustomError('message')
       Traceback (most recent call last):
       CustomError: message
 
-      >>> raise CustomError('message') #doctest: +IGNORE_EXCEPTION_DETAIL
+      >>> raise CustomError('message')
       Traceback (most recent call last):
       my_module.CustomError: message
 
@@ -569,7 +569,7 @@ doctest decides whether actual output matches an example's expected output:
    earlier (those releases do not support :ref:`doctest directives
    <doctest-directives>` and ignore them as irrelevant comments). For example::
 
-      >>> (1, 2)[3] = 'moo' #doctest: +IGNORE_EXCEPTION_DETAIL
+      >>> (1, 2)[3] = 'moo'
       Traceback (most recent call last):
         File "<stdin>", line 1, in ?
       TypeError: object doesn't support item assignment