UPDATE "#__mail_templates"
   SET "params" = '{"tags":["name","sitename","siteurl","username"]}'
 WHERE "template_id" = 'com_users.registration.user.registration_mail' AND "params" = '{"tags":["name","sitename","activate","siteurl","username"]}';

UPDATE "#__mail_templates"
   SET "params" = '{"tags":["name","sitename","siteurl","username","password_clear"]}'
 WHERE "template_id" = 'com_users.registration.user.registration_mail_w_pw' AND "params" = '{"tags":["name","sitename","activate","siteurl","username","password_clear"]}';