Improve `test_descr.test_not_implemented`

[sobolevn]

Bug report

Right now there are several problems that can be attributed to the long history of this test.

1. operator name here is not needed:

   cpython/Lib/test/test_descr.py

   Line 4604 in 396b831

   exec(expr, {'x': x, 'y': y, 'operator': operator})

2. rname here is not used:

   cpython/Lib/test/test_descr.py

   Line 4629 in 396b831

   rname = '__r' + name[2:]

   This means that __r*__ methods are not tested. They were removed 18 years ago in 4886cc3#diff-6b813570d02ae3544e7e0233ae21d647f8e2dc47486495557e8d16c80460e85b I think that adding them back is a good thing

Linked PRs

• gh-117797: Improve test_descr.test_not_implemented #117798
• [3.12] gh-117797: Improve test_descr.test_not_implemented (GH-117798) #117921