This pull request reverses a recent change to Belgian salary contract mobility budget calculations. The update is being held back from this version so key users can validate it first in the main development version before it reaches this release line.

This reverts commit [692ecf81fe97d86d2f3196456dbb57ced90fe83c.](https://github.com/odoo/enterprise/pull/109845)

Mobility budget should be done in master only to allow pre-testing by key users

Task-6389002