compat_openssl: fix for LibreSSL 4.1.0

orbearequested to merge
orbea/tor:libressl into main

Starting with LibreSSL 4.1.0 this now causes a build failure:

src/lib/tls/tortls_openssl.c: In function 'tor_tls_setup_session_secret_cb':
src/lib/tls/tortls_openssl.c:1059:39: error: passing argument 2 of 'SSL_set_session_secret_cb' from incompatible pointer type [-Wincompatible-pointer-types]
 1059 |   SSL_set_session_secret_cb(tls->ssl, tor_tls_session_secret_cb, NULL);
      |                                       ^~~~~~~~~~~~~~~~~~~~~~~~~
      |                                       |
      |                                       int (*)(SSL *, void *, int *, struct stack_st_SSL_CIPHER *, SSL_CIPHER **, void *) {aka int (*)(struct ssl_st *, void *, int *, struct stack_st_SSL_CIPHER *, struct ssl_cipher_st **, void *)}
In file included from src/lib/tls/tortls_openssl.c:48:
/usr/include/openssl/ssl.h:1489:30: note: expected 'tls_session_secret_cb_fn' {aka 'int (*)(struct ssl_st *, void *, int *, struct stack_st_SSL_CIPHER *, const struct ssl_cipher_st **, void *)'} but argument is of type 'int (*)(SSL *, void *, int *, struct stack_st_SSL_CIPHER *, SSL_CIPHER **, void *)' {aka 'int (*)(struct ssl_st *, void *, int *, struct stack_st_SSL_CIPHER *, struct ssl_cipher_st **, void *)'}
 1489 |     tls_session_secret_cb_fn tls_session_secret_cb, void *arg);
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~

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