[FIX] calendar: avoid creation of the document on invitation

Install Projects, documents, calendar, website, crm.
Under Settings enable "File Centralization"
Now go to Projects, enter in a Task, click on "schedule activity".
On the activity form under "Activity Type" choose Meeting, click on
"Open Calendar" button.
Choose a slot, edit the event, add a contact type individual, save
Error will popup.

This is caused by the whole flow of creating a new document for the
invitation.ics generated for the meetings which has to be sent via email
but get detected as an attachment to be sent into the document app as
well.

Disabling the document creation since it is not a relevant attachment

opw-2150770

closes odoo/odoo#43341

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