Add same change to description for findOne

lib/persisted-model.js

@@ -812,7 +812,9 @@ module.exports = function(registry) {
       accepts: [
         {arg: 'filter', type: 'object', description:
         'Filter defining fields, where, include, order, offset, and limit - must be a ' +
-        'JSON-encoded string ({"something":"value"})'},
+        'JSON-encoded string ({"where":{"something":"value"}}).  ' +
+        'See https://loopback.io/doc/en/lb3/Querying-data.html#using-stringified-json-in-rest-queries ' +
+        'for more details.'},
         {arg: 'options', type: 'object', http: 'optionsFromRequest'},
       ],
       returns: {arg: 'data', type: typeName, root: true},