Update the auto-deploy branch creation cadence

Why is this change being made?

We are increasing the frequency of creating the branches for deployment to gitlab.com with gitlab-com/gl-infra/delivery#627 (closed) . This updates the release handbook page to reflect the status.

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