Update prod dev. workflow to clarify release post

Why is this change being made?

The product development workflow says that the PM is responsible for merging the release post item. It's actually the EM, but more importantly this MR points to the MR template to ensure we have a SSOT.

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