[issue37408] [DOC] Precise that Tarfile "format" argument only concerns writing.

[Roundup Robot]

Change by Roundup Robot <devnull at psf.upfronthosting.co.za>:


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keywords: +patch
pull_requests: +14203
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/14389

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue37408>
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