textarea is not a valid json_schema anymore

Problem/Motivation

Some of the Tugboat environments with projects that has canvas RC started to fail with this error:

The website encountered an unexpected error. Try again later.
InvalidArgumentException: modules/contrib/canvas does not contain a `textarea` definition. in Drupal\canvas\JsonSchemaDefinitionsStreamwrapper->stream_open() (line 58 of modules/contrib/canvas/src/JsonSchemaDefinitionsStreamwrapper.php).

After investigating, it seems that the starshot_demo theme has many instances of json-schema-definitions://canvas.module/textarea that must be deleted in order to make it work again.

The textarea removal happened here: https://www.drupal.org/project/canvas/issues/3520843 📌 Remove backwards compatibility with "Text area" prop in code editor, superceded by "Formatted text" Postponed

Steps to reproduce

Follow the steps in https://www.drupal.org/drupalorg-issue-fork-tugboat-preview-log/68ece34f... → .
In short:

composer require  drupal/demo_design_system  drupal/components  drupal/default_content
drush si standard 
drush --yes pm:install canvas media_library components default_content
drush theme:enable starshot_demo
drush --yes config:set system.theme default starshot_demo
drush updb # Here comes the error

Proposed resolution

Adapt the $ref: json-schema-definitions://canvas.module/textarea to the proper option.