GH-97950: Use new-style index directive ('object') (GH-104158)
* Uncomment object removal in pairindextypes
* Use new-style index directive ('object') - C API
* Use new-style index directive ('object') - Library
* Use new-style index directive ('object') - Reference
* Use new-style index directive ('object') - Tutorial
(cherry picked from commit 6ab463684b)
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
I think that none of these API calls can fail, but only few of them are
documented as such. Add the sentence "This function always succeeds" (which is
the same already used e.g. by PyNumber_Check) to all of them.
