Update plugins.md

The `__destruct` is excluded (just like `__construct`), see `\Magento\Framework\Interception\Code\Generator\Interceptor::_getClassMethods()`

Author: pmzandbergen

src/guides/v2.3/extension-dev-guide/plugins.md

@@ -18,7 +18,7 @@ Plugins can not be used on following:
 *  Final classes
 *  Non-public methods
 *  Class methods (such as static methods)
-*  `__construct`
+*  `__construct` and `__destruct`
 *  Virtual types
 *  Objects that are instantiated before `Magento\Framework\Interception` is bootstrapped