[FIX] web_editor: parallax effect in sanitized field

A sanitize fields by default remove all attributes outside of a
whitelist (if sanitize_attributes on field is not set to false).

This prevent to use parallax widget in Html sanitized field since
attribute "data-scroll-background-ratio" define parallax effect speed
but was not in whitelist.

note: also keep data-interval for gallery widget

opw-2053983
closes #35961

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>