Change /metallb to Historical

[xmulligan]

Repository URL

https://github.com/cilium/metallb

Current Scope

Ecosystem

Proposed Scope

Historical

Motivation for Request

We don't use metallb in the project anymore because it was replaced by native Cilium functionality. We should archive the repo

Code of Conduct

• I agree to follow Cilium's Code of Conduct

To be filled by a Cilium committer

• Approved change of scope is reflected in REPOSITORIES.md