AjaxResponse::getCommands has wrong return type

Problem/Motivation

The method AjaxResponse::getCommands claims it is going to return \Drupal\Core\Ajax\CommandInterface[].

This is not the case. $commands in that class are going to be an array of return values from \Drupal\Core\Ajax\CommandInterface::render (which in turn has the following description: Return an array to be run through json_encode and sent to the client.)

Proposed resolution

Change the doc comment

Remaining tasks

Write a patch

User interface changes

None

API changes

None

Data model changes

None

Release notes snippet

N/A