Remove confDH_PARAMETERS settings in favor of using sendmail's built-in

default which was added in sendmail 8.15.2 (the config line predates
that 8.15.2 feature).  This also alleviates the need for admins
to create the DH parameters file if they opt to use Diffie-Hellman.

PR:		248387
MFC after:	2 weeks

etc/sendmail/freebsd.mc

@@ -66,7 +66,6 @@ define(`confCLIENT_CERT', `CERT_DIR/host.cert')dnl
 define(`confCLIENT_KEY', `CERT_DIR/host.key')dnl
 define(`confCACERT', `CERT_DIR/cacert.pem')dnl
 define(`confCACERT_PATH', `CERT_DIR')dnl
-define(`confDH_PARAMETERS', `CERT_DIR/dh.param')dnl
 
 dnl Uncomment to allow relaying based on your MX records.
 dnl NOTE: This can allow sites to use your server as a backup MX without