[FIX] account: avoid hiding 'Amount Matching'

Go to Reconciliation Models > Invoices Matching Rule
Set the parameter 'Amount Matching'
Set 'Partner Is Set & Matches'
Save
Edit
Unset 'Partner Is Set & Matches'

'Amount Matching' will switch to invisible but is not disabled.
Removing the invisibility check so that the field is always
editable

This also reverts commit 61f1ca63.
Due to a misunderstanding this solution was chosen while the real
intention was to always show the field

opw-2261134

closes odoo/odoo#52264

Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>