[FIX] *: adapt odoo interface violet

Change color #a24689 to #875A7B

Commit https://github.com/odoo/enterprise/commit/8ac1c19fac7615fecd51e670f798d13158a4e53c
changed the odoo interface violet by changing the main LESS variable
but forgot there was many direct occurences in XML/HTML/... (for
example for the mobile browser color).

Even if it's community the odoo interface violet is used at many places
(module description, XML demo data, ...).