ParagraphsBehaviorInterface::settingsIcon() claims to return string[], but TestBoldTextBehavior::settingsIcon() does not return string[]

Problem/Motivation

ParagraphsBehaviorInterface::settingsIcon(), in its DocBlock, says this:

   * @return string[]
   *   The plugin settings.

However TestBoldTextBehavior::settingsIcon() contains this code:

     return [
        'bold' => [
          '#theme' => 'paragraphs_info_icon',
          '#message' => $this->t('Bold: Yes.'),
          '#icon' => 'bold',
        ],
      ];

This is not of type string[].

Proposed resolution

Document that settingsIcon should return an associative array, not an array of strings.

Remaining tasks

User interface changes

API changes

Data model changes