add section for the normalization smartcampaigns in marketo

Why is this change being made?

Add more information about the process that are running in Marketo so other Ops team members are able to maintain.

Also to provide better context to other teams that might be impacted by these workflows & data that result from them.

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

/close https://gitlab.com/gitlab-com/marketing/marketing-operations/issues/1877