Promote consistency between PMs for release blog

Why is this change being made?

As per Product Operations Office Hours 2020-02-12 https://docs.google.com/document/d/1uVoUBjZasSBkmKJRGRY6GN_Gg31uiI8byLxX7cV0kmE/edit#heading=h.y7ts8yofb4o7

It was identified there was not a good recommended baseline for what belongs in a marketing release blog post and what does not, and there is a potential scope creep, and so I would like to start the discussion and documentation of that baseline consistency between Product Managers and it was recommended that the guidance (not requirements because that is too rigid) vary by maturity level.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what