[FIX] mail: missing dependency for icon in public

The right arrow icon on the public page relies on odoo-ui.
Currently, this file is not correctly imported into the public bundle, since
the icon is not showing.

This fix is to import the essential file into the public bundle.

closes odoo/odoo#138354

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/__manifest__.py

@@ -174,6 +174,7 @@ For more specific needs, you may also assign custom-defined actions
         ],
         'mail.assets_public': [
             'web/static/lib/jquery/jquery.js',
+            'web/static/lib/odoo_ui_icons/style.css',
             'web/static/src/libs/fontawesome/css/font-awesome.css',
             ('include', 'web._assets_helpers'),
             ('include', 'web._assets_backend_helpers'),