docs(schematype): document SchemaType#doValidate()

Author: vkarpov15

lib/schematype.js

@@ -1242,7 +1242,7 @@ SchemaType.prototype.select = function select(val) {
  * @param {any} value
  * @param {Function} callback
  * @param {Object} scope
- * @api private
+ * @api public
  */
 
 SchemaType.prototype.doValidate = function(value, fn, scope, options) {