storage: remove usage of secret placeholder

src/dns/interface.js

@@ -20,13 +20,13 @@ const assert = require('node:assert'),
     BoxError = require('../boxerror.js');
 
 function removePrivateFields(domainObject) {
-    // in-place removal of tokens and api keys with constants.SECRET_PLACEHOLDER
+    // in-place removal of tokens and api keys
     return domainObject;
 }
 
 // eslint-disable-next-line no-unused-vars
 function injectPrivateFields(newConfig, currentConfig) {
-    // in-place injection of tokens and api keys which came in with constants.SECRET_PLACEHOLDER
+    // in-place injection of tokens and api keys
 }
 
 // replaces any existing records or creates new records of subdomain+type with values