bpo-42747: Remove Py_TPFLAGS_HAVE_AM_SEND and make Py_TPFLAGS_HAVE_VERSION_TAG no-op (GH-27260) (GH-27306)

* Remove code that checks Py_TPFLAGS_HAVE_VERSION_TAG

    The field is always present in the type struct, as explained
    in the added comment.

* Remove Py_TPFLAGS_HAVE_AM_SEND

    The flag is not needed, and since it was added in 3.10 it can be removed now.
(cherry picked from commit a4760cc32d9e5dac7be262e9736eb30502cd7be3)

Co-authored-by: Petr Viktorin <encukou@gmail.com>
7 files changed