This update removes outdated internal test support files from the Planning app that relied on legacy bus testing helpers. It helps keep the codebase easier to maintain and reduces reliance on obsolete testing infrastructure, with no expected impact on day-to-day users.

Purpose of this commit:
Remove files that depends on legacy 'bus/../test/helpers'.

Part of:3818666

This update ensures our LinkedIn integration uses the latest LinkedIn API version (202411). This upgrade maintains compatibility with LinkedIn's platform and improves the reliability of our social media connections. No new features were added, and the changes are focused on updating API headers as documented by LinkedIn.

This commit upgrades the Linkedin's versioned API to the latest available which is `202411`.

As no features has been broken, nor is there any new features impacting the parts of the API we use. Only the headers are updated as explained inside their documentation.

task-4273179

Forward-Port-Of: odoo/enterprise#74687