gh-94172: Remove ssl.PROTOCOL_SSLv2 dead code

[vstinner]

Remove dead code related to ssl.PROTOCOL_SSLv2. ssl.PROTOCOL_SSLv2
was already removed in Python 3.10.

In test_ssl, @requires_tls_version('SSLv2') always returned False.

Extract of the removed code: "OpenSSL has removed support for SSLv2".

• Issue: Remove deprecated keyfile, certfile and check_hostname parameters, in favor of context #94172

[vstinner]

vstinner added the skip news label now

The only effect for end users is the removal of the documentation. The ssl.PROTOCOL_SSLv2 constant was already removed in Python 3.10.

[vstinner]

On Fedora 36, OPENSSL_NO_SSL3 is defined by /usr/include/openssl/configuration-x86_64.h. This file is documented as:

OpenSSL was configured with the following options

It seems like disabling SSLv3 is still a configuration option in OpenSSL 3.0.3.

For me, it's not obvious that Python no longer supports SSLv3. It seems to depend if SSLv3 was disabled in OpenSSL configuration (when OpenSSL was built).

Python ssl.SSLContext() sets SSL_OP_NO_SSLv3 option, unless protocol=PY_SSL_VERSION_SSL3.

[vstinner]

cc @tiran

[vstinner]

Follow-up: issue #94377 "ssl: Drop support for unsafe SSLv3 protocol, remove ssl.PROTOCOL_SSLv3".