[FIX] base: fix password edition modal weird design

This commit removes an unwanted `bg-primary` class applied to the change
password modal, making it weird and unconsistent regarding others modals
across Odoo.

=========
Steps to reproduce
=========

> Open a database
> Click on your avatar in the top right corner
> Click on `Preferences`
> Go to `Account Security`
> Click on `Change password`

>> The modal has a `bg-primary` class, making it look purple.

task-3836699

closes odoo/odoo#160462

X-original-commit: 2813540aba7556b915185e482cbb6d9500db7af1
Signed-off-by: Chrysanthe Gomrée (chgo) <chgo@odoo.com>
Signed-off-by: Pierre Paridans (app) <app@odoo.com>

odoo/addons/base/static/src/scss/res_partner.scss

@@ -14,3 +14,9 @@
         --gutter-x: 0;
     }
 }
+
+// This is an ugly workaround to prevent having ugly borders in the Password confirmation dialog
+// TODO: remove me in master
+.modal .o_form_view .o_form_sheet_bg.bg-primary {
+    --background-color: #{$o-view-background-color};
+}

odoo/addons/base/views/res_users_identitycheck_views.xml

@@ -6,7 +6,7 @@
             <field name="model">res.users.identitycheck</field>
             <field name="arch" type="xml">
                 <form string="Password Confirmation">
-                    <sheet class="bg-primary">
+                    <sheet>
                         <h3><strong>Please enter your password to confirm you own this account</strong></h3>
                         <div>
                             <field class="o_field_highlight col-10 col-md-6 px-0" name="password" autocomplete="current-password"