In the HTTP(S) test server in the core tests, use
`ssl.SSLContext.wrap_socket`, not `ssl.wrap_socket`. The latter emits a
`DeprecationWarning` since Python 3.10 and is [removed in Python
3.12](https://github.com/python/cpython/issues/94199).
This fixes the core tests (but not necessarily the `grpcio` tests) for
Python 3.12.
This is relevant to https://github.com/grpc/grpc/issues/33063.