[3.8] bpo-39674: Update collections ABC deprecation doc by vstinner · Pull Request #18748 · python/cpython

The deprecation originally slated for 3.9 was deferred to 3.10
(bpo-39674, pythonGH-18545) and the documentation on the 3.8 release was
updated accordingly (pythonGH-18748). However the deprecation notice in
the code was left as is, and still indicates deprecation with 3.9.

The deprecation originally slated for 3.9 was deferred to 3.10
(bpo-39674, GH-18545) and the documentation on the 3.8 release was
updated accordingly (GH-18748). However the deprecation notice in
the code was left as is, and still indicates deprecation with 3.9.