Call to undefined method Drupal\content_kanban\Plugin\DashboardBlock\RecentKanbanActivities::t() in Drupal\content_kanban\Plugin\DashboardBlock\RecentKanbanActivities->composeMessage()

Problem/Motivation

Upon visiting /admin/content-planner/dashboard I get the following error: "Error: Call to undefined method Drupal\content_kanban\Plugin\DashboardBlock\RecentKanbanActivities::t() in Drupal\content_kanban\Plugin\DashboardBlock\RecentKanbanActivities->composeMessage() (line 196 of modules/contrib/content_planner/modules/content_kanban/src/Plugin/DashboardBlock/RecentKanbanActivities.php)."

The issue is caused by the use of "$this->t(" in RecentKanbanActivities class, because StringTranslationTrait isn't imported.

Proposed resolution

Similar to how a few other contrib modules solved this issue, I propose using StringTranslationTrait to avoid this issue.