Bug 30567: Fix price formatting when adding a manual invoice with CurrencyFormat FR

Bug 30567: Fix price formatting when adding a manual invoice with CurrencyFormat FR

In input fields we always use the decimal . while the display format
uses the decimal separtor definded by CurrencyFormat. When adding a
manual invoice without this patch, the amount is shown with comma, but
it should be . in the input field.

To test:
1- Go in Administration->Debit types
2- Click on New debit type
3- Fill the form:
   Code: USEDBOOK
   Default amount: 0.50
   Description: Used book
   Can be manually invoiced: Yes
4- Save
5- Go to any patron account
6- Go to the "Accounting" tab
7- Click on "Create manual invoice"
8- Fill the form
9- Choose the created debit (Used book)
10- Verify that the format is incorrect (0,50 instead of 0.50)
11- Apply the patch
12- Verify the amount is now using the correct format

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>