[3.13] gh-141004: Document `PyErr_ProgramTextObject` and `PyErr_ProgramText` (GH-141250) (GH-141257)

gh-141004: Document `PyErr_ProgramTextObject` and `PyErr_ProgramText` (GH-141250)
(cherry picked from commit be1c72a45d54cdd35e0a830e18224c4c74be808c)

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>
Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>