Update ajax.tasks.php

Change to make one translation less since `%s is currently assigned to <b>%s</b>` is already used in ajax.tasks.php and ajax.tickets.php

include/ajax.tasks.php

@@ -529,7 +529,7 @@ class TasksAjaxAPI extends AjaxController {
                     $target ? "/$target" : ''),
                 );
         if ($task->isAssigned()) {
-            $info['notice'] = sprintf(__('%s is currently assigned to %s'),
+            $info['notice'] = sprintf(__('%s is currently assigned to <b>%s</b>'),
                     __('Task'),
                     $task->getAssigned());
         }