[Python] Wheel / sdist build uses docstrings generation script we don't want to distribute

[rok]

Describe the enhancement requested

See discussion on #49235

[..] the question boils down to: would some people like to get the docstrings from the sdist, or not?
This is probably a matter how the sdist is being used at all: if it's only an intermediate step for building a wheel, then the docstrings can be generated when building a wheel. If the sdist is sometimes used as an end product of itself, then it might be better to ship the docstrings in the sdist.

Component(s)

Python