[IMP] accounting: split deferred settings

[RicGR98]

This has been done in the following commit
https://github.com/odoo/enterprise/commit/39fffc5541eb51d7a3ae25405abe90fe6031001a

[robodoo]

This PR targets the disabled branch odoo/documentation:saas-17.3, it needs to be retargeted before it can be merged.

[robodoo]

[dade-odoo]

Hey @RicGR98 , as always thanks for keeping our accounting documentation up to date! I have two questions:

1. In the Configuration sections of each doc, it looks like you removed the wrong lines for each - the deferred revenue doc includes the line explaining deferred expenses and vice versa. Was that a mistake or am I misunderstanding something?
2. I see the value of Full Months is available for the Based on field. Could you add a brief explanation of how that would work (what makes it different from just Months)?
   Thanks!