[IMP] hr_contract: rename 'Contract Type' into 'Employee Category'
[IMP] hr_contract: rename 'Contract Type' into 'Employee Category'

Purpose :
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On the Contract form view the field label for the "contract type" is "Employee Category".

Then it will be good if we keep the same label on the group by also...

Right now on the Group By it is "Contract Type"

closes odoo/odoo#27560
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo