[FIX] payment_mollie: neutralize mollie token

before this commit, on neutralizing the database the
mollie token is not cleared from the payment provider.

after this commit, on neutralizing a database, the
token from mollie payment provider is cleared.

closes odoo/odoo#125296

Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>

addons/payment_mollie/data/neutralize.sql

+-- disable mollie payment provider
+UPDATE payment_provider
+   SET mollie_api_key = NULL;