[openssl/openssl] 6220d0: Add a deprecation warning for a function in docs

[Kevin J.]

  Branch: refs/heads/openssl-3.0
  Home:   https://github.com/openssl/openssl
  Commit: 6220d0a7ac9309c1271a8a09d8551d95e7d5b857
      https://github.com/openssl/openssl/commit/6220d0a7ac9309c1271a8a09d8551d95e7d5b857
  Author: Kevin Jerebica <jerebicakevin at gmail.com>
  Date:   2024-01-18 (Thu, 18 Jan 2024)

  Changed paths:
    M doc/man3/SSL_get_peer_certificate.pod

  Log Message:
  -----------
  Add a deprecation warning for a function in docs

The function in question is SSL_get_peer_certificate()

CLA: trivial

Reviewed-by: Tom Cosgrove <tom.cosgrove at arm.com>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23315)

(cherry picked from commit 3e938453be47751d50917e25b8f7334b482844b3)