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_get_extms_support.pod b/doc/man3/SSL_get_extms_support.pod
index ba4de3a..9719c0a 100644
--- a/doc/man3/SSL_get_extms_support.pod
+++ b/doc/man3/SSL_get_extms_support.pod
@@ -26,7 +26,7 @@
 
 =head1 SEE ALSO
 
-L<ssl(3)>
+L<ssl(7)>
 
 =head1 COPYRIGHT