Fix referenses in section 3 manuals

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1900)
diff --git a/doc/man3/SSL_set_session.pod b/doc/man3/SSL_set_session.pod
index 1de533f..6130355 100644
--- a/doc/man3/SSL_set_session.pod
+++ b/doc/man3/SSL_set_session.pod
@@ -53,7 +53,7 @@
 
 =head1 SEE ALSO
 
-L<ssl(3)>, L<SSL_SESSION_free(3)>,
+L<ssl(7)>, L<SSL_SESSION_free(3)>,
 L<SSL_get_session(3)>,
 L<SSL_session_reused(3)>,
 L<SSL_CTX_set_session_cache_mode(3)>