fix(issue): restrict tech group search option to assignable groups

Author: btry

inc/issue.class.php

@@ -700,6 +700,7 @@ public function rawSearchOptions() {
          'massiveaction'      => false,
          'nodisplay'          => $hide_technician,
          'nosearch'           => $hide_technician,
+         'condition'          => ['is_assign' => 1],
          'joinparams'         => [
             'beforejoin'         => [
                'table'              => Group_Ticket::getTable(),