v4.6.4

This is a security release.

• Fix stored cross-site scripting in the order details shown on the checkout
  confirmation step and the order page.
  Spree::OrdersHelper#truncated_product_description rendered product
  descriptions as raw HTML. See
  GHSA-87gm-56c6-255g.

All stores using solidus_frontend should upgrade. The product page is fixed
separately in solidus_core 4.6.4; see
GHSA-x943-j5hw-mr2w.