ci: remove harden-runner

[sjinks]

Description

This PR removes harden-runner because, in the current configuration, it is useless:

1. It needs to be maintained (this repo uses a very outdated version).
2. The list of domains needs to be reviewed from time to time.
3. All jobs must be guarded,

Pre-review checklist

Please make sure the items below have been covered before requesting a review:

• This change works and has been tested locally or in Codespaces (or has an appropriate fallback).
• This change has relevant unit tests (if applicable).
• This change has relevant documentation additions / updates (if applicable).
• I've created a changelog description that aligns with the provided examples.

Pre-deploy checklist

• VIP staff: Ensure any alerts added/updated conform to internal standards (see internal documentation).

Steps to Test

N/A