Fix the style of an array de-allocation in dnssec-cds

Mention the element size explicitly, so that `matching_sigs()`,
`signed_loose()`, and `signed_strict()` use the same calculation.

bin/dnssec/dnssec-cds.c

@@ -739,7 +739,7 @@ signed_strict(dns_rdataset_t *dsset, dns_secalg_t *algo) {
 		}
 	}
 
-	isc_mem_put(mctx, algo, nkey);
+	isc_mem_put(mctx, algo, nkey * sizeof(algo[0]));
 	return (all_ok);
 }