removed based on samdark's comment from https://github.com/yiisoft/yii2/pull/1485/files#r8293528

docs/guide/extensions.md

@@ -5,7 +5,6 @@ Code style
 ----------
 
 - Extension code style SHOULD be similar to [core framework code style](https://github.com/yiisoft/yii2/wiki/Core-framework-code-style).
-- In case of using getter and setter for defining a property it's preferred to use method in extension code rather than property.
 - All classes, methods and properties SHOULD be documented using phpdoc. Note that you can use markdown and link to properties and methods
 using the following syntax: e.g. `[[name()]]`, `[[name\space\MyClass::name()]]`.
 - If you're displaying errors to developers do not translate these (i.e. do not use `\Yii::t()`). Errors should be