This update aligns Belgian payroll and salary holiday demo data with the newer leave type color field. It helps keep sample and test data compatible with the latest HR leave setup, reducing maintenance issues without changing day-to-day user workflows.

As part of https://github.com/odoo/odoo/pull/99804, the color_name field is remove from the hr.leave.type model and replaced by color.
This commit removes color_name from the demo data.

task-2963752
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Payroll holiday attests now include a gross pay amount, giving Belgian payroll teams clearer salary information when preparing employee departure documents. This improves the completeness of holiday attest reporting and helps reduce manual lookup or calculation work.

TaskID: 2984604