[ssl] Remove deprecated protocols, OP_NO_TLS/SSL, and support for TLS < 1.2

[tiran]

Feature or enhancement

Python 3.10 or earlier versions of Python have deprecated

• all PROTOCOL_* constants except PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_CLIENT
• SSLContext without a protocol parameter
• all OP_NO_TLS* and OP_NO_SSL* options
• support for SSL 2.0, SSL 3.0, TLS 1.0, and TLS 1.1

It is time to remove the constants and features.

[vstinner]

support for SSL 2.0

It was removed in Python 3.10, no?

[tiran]

There was still a bit of SSLv2 code left.