Update OEP-45 ADR-2 to reflect current reality

[sarina]

OEP-45 ADR-2 under Implementation Strategy it states:

Once this ADR has reached Provisional status:

• A new repository will be created on GitHub, e.g. at openedx/openedx-helm-charts
• The authors of this ADR will create a roadmap using GitHub Issues by defining the initial development issues.
• Invite interested parties to become core contributors on the repo, and nominate some of them.
• Participating core contributors will then complete the roadmap and begin developing an MVP.

The ADR is marked as Accepted, so this text should be updated. I note that the repo openedx-helm-charts does not exist, should this link be the Harmony repo?

cc @bradenmacdonald @felipemontoya @kdmccormick as authors/approvers in #372