Added policy about not using group email address for a GitLab support account

Why is this change being made?

People should not use shared (group) email addresses for a GitLab support account. There are security problems: people who leave the company could still have access; actions taken via the shared address are hard to trace to a responsible individual. In addition, group email addresses may often have automated responses or other behaviors attached to them, which causes problems such as Zendesk opening extra tickets as a result of an automated response. So, this new policy is the first step in preventing people from using group email addresses when working with GitLab Support.

How will this merge request impact page speed?

No expected impact on page speed.

Does this MR meet the acceptance criteria?

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• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

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