[FIX] base_setup, calendar, point_of_sale, stock: update doc URLs

This commit updates the documentation URLs to the current URLs, although
there are already redirect rules in place as fallback.

Related odoo/documentation pull requests:

Calendar:
https://github.com/odoo/documentation/pull/4032
task-3217827

POS
https://github.com/odoo/documentation/pull/4226
task-3284514

Inventory
https://github.com/odoo/documentation/pull/2556



closes odoo/odoo#119824

Related: odoo/enterprise#40372
Signed-off-by: Raphael Collet <rco@odoo.com>