[FIX] sale_timesheet_purchase: remove uninstall_hook

The commit f3999314af introduces a
declaration of non-existing `uninstall_hook` in the manifest, causing
error when trying to uninstall the sale_timesheet_purchase module.
This commit simply removes it.

Task #2039731

closes odoo/odoo#35106

Signed-off-by: Simon Lejeune (sle) <sle@openerp.com>

addons/sale_timesheet_purchase/__manifest__.py

@@ -13,5 +13,4 @@ Allows to access purchase orders from Project Overview
     'data': [],
     'demo': [],
     'auto_install': True,
-    'uninstall_hook': 'uninstall_hook',
 }