openssh: Request the OpenSSL 1.1 API

Upstream OpenSSH commit f51423bda ("request 1.1x API compatibility for
OpenSSL >=3.x") requests OPENSSL_API_COMPAT version 0x10100000L (OpenSSL
1.1.0), in order to avoid warnings about deprecated functions.

Do the same here, to avoid getting those warnings.

Reviewed by: emaste
Approved by: emaste (mentor)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D49517