Uninstall impossible, without disabling text format first

Encountered this will debugging another issue.

## Test

1. Install Drupal
2. Install Drush

composer required drush/drush

3. Install Gutenberg

composer required drupal/gutenberg

4. Enable Gutenberg

$ drush en gutenberg
 [success] Successfully enabled: gutenberg

5. Disable Gutenberg

$ drush pmu gutenberg
In PmCommands.php line 211:                                                                                                                           
  gutenberg: Provides a filter plugin that is in use in the following filter formats: <em class="placeholder">Gutenberg Blocks text format</em>  
                                                                                                                                                 

It is actually related to a Core issue #2635728: Uninstalling a module providing display extenders causes fatal errors → and might happen with other modules (that provides text filters) as well.

In #3204782: Uninstalling Gutenberg editor broke site → we implemented such a routine, but unfortunately the Drupal core config validation (your error) is triggered before gutenberg_uninstall(). So manual steps would be to disable the Gutenberg text filter on all text formats that are using it (most likely only the Gutenberg text format) and afterwards uninstall the module.