LenientConfigSchemaChecker shows its link as escaped HTML

Problem/Motivation

In LenientConfigSchemaChecker:

      $message = sprintf('%s. These errors mean there is configuration that does not comply with its schema. This is not a fatal error, but it is recommended to fix these issues. For more information on configuration schemas, check out <a href="%s">the documentation</a>.', $exception->getMessage(), 'https://www.drupal.org/docs/drupal-apis/configuration-api/configuration-schemametadata');

      $this->messenger->addWarning($message);

This warning message's link shows as raw HTML in the message.

(also 'check out'?? urgh!)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet