[docs] [issue23220] IDLE: Document how Shell displays user code output

[Tal Einat]

Change by Tal Einat <taleinat at gmail.com>:


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pull_requests: +14939
pull_request: https://github.com/python/cpython/pull/15211

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue23220>
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