Place $5k limit on security questionnaires

Why is this change being made?

Demand for security questionnaires has been too voluminous to handle. There has been a noticeable surge in low ACV requests, and often-times these are being asked to be prioritized the same as high ACV requests.

Because GitLab is so Transparent, much of the information on these questionnaires is publicly available in either docs.gitlab.com, about.gitlab.com, or about.gitlab.com/handbook; often the security team is serving as a data entry team for the requester.

To go along with this change, the security team is developing additional sales-enablement collateral which will be made available this quarter.

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