[docs] [issue30312] Small correction in set code sample

[Raymond Hettinger]

Raymond Hettinger added the comment:

ISTM the result of the expression makes the meaning clear:

    >>> a | b
    {'r', 'l', 'b', 'c', 'z', 'd', 'a', 'm'}

That said, the text might be a little clearer like this:

   # letters in a or b or both

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assignee: docs at python -> Mariatta
nosy: +Mariatta, rhettinger
priority: normal -> low

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue30312>
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