chore: Updates the name of the repository containing SD-Core root modules

[Gmerold]

Description

This PR updates the name of the repository containing SD-Core root modules. We're loosing the -k8s suffix, because the repo will also hold the root module for the machine charm.

NOTE: The repo hasn't been renamed yet, so please don't merge this PR.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [x] I have added tests that validate the behaviour of the software
• [x] I validated that new and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have bumped the version of the library