RT4019: Duplicate -hmac flag in dgst.pod

Signed-off-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NEmilia Käsper <emilia@openssl.org>

doc/apps/dgst.pod

@@ -13,7 +13,6 @@ B<openssl> B<dgst>
 [B<-hex>]
 [B<-binary>]
 [B<-r>]
-[B<-hmac arg>]
 [B<-non-fips-allow>]
 [B<-out filename>]
 [B<-sign filename>]
@@ -64,10 +63,6 @@ output the digest or signature in binary form.
 
 output the digest in the "coreutils" format used by programs like B<sha1sum>.
 
-=item B<-hmac arg>
-
-set the HMAC key to "arg".
-
 =item B<-non-fips-allow>
 
 Allow use of non FIPS digest when in FIPS mode.  This has no effect when not in