[FIX] account: restricted fields on notes

In 13.0, some account.move.line fields (amount_currency, debit, credit
and account_id) couldn't have a value when the line is of type 'note'.
Skiping them during line copy for notes is not an issue.

During 12.0->13.0 migration, we were facing issues with "grouped similar
invoice lines in a single move line", because this feature is not
available anymore in 13.0. To avoid any "loss of data" during migration,
we used lines of type note to create "missing" invoice lines in move
lines without altering accounting in any way. As a consequence, we have
13.0 databases with lines of type note having values for fields who
couldn't have ones.

closes odoo/odoo#64055

Signed-off-by: Quentin De Paoli (qdp) <qdp@openerp.com>