Webform 6.3.x submission list displays workflow information as HTML code

Problem/Motivation

Webform submission list display HTML source code in the Workflow column with Webform 6.3.x:

WebformCompositeBase switched from #markup to #plaintext when rendering formatHtmlItemValue() string return value.

Steps to reproduce

Create a webform submission on a workflow-enabled webform and check the submission list.

Proposed resolution

Check MR.