Move to clean-lang.org

What does this MR do?

Updates this repository to use clean-lang.org instead of clean-nc.camilstaps.nl

To do:

• iTasks needs to be published in the registry for the rank settings constraints to work.

Changes to public APIs

None.

Author's checklist (required)

See https://gitlab.com/clean-nc/contributing#isocyanoclean-contributing-guidelines for the rationale behind these items:

• The commit history does not contain merges (use git rebase -i main if it does)
• Intermediate commits compile (use git rebase -i main if not)
• Newly added code has a style consistent with the rest of the repository
• Newly added code is documented
• If bugs have been solved, tests have been added

Related issues

None.