[issue31907] doc: Clarify error message when attempting to call function via str.format()

[Irit Katriel]

Change by Irit Katriel <iritkatriel at yahoo.com>:


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keywords: +patch
pull_requests: +23801
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/25053

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue31907>
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