Exclude issue related to personal data leak from disclosure policy

Why is this change being made?

Issues related to personal data leak are not disclosed. However this is not mentioned in the disclosure policy. This change is update the disclosure policy to call out that issue related to personal data leak are not disclose. The disclosure policy is for disclosing product security issues however issues related personal data leak through issues or attachments or other means does not fall in that category.

Related internal discussion https://gitlab.com/gitlab-com/gl-security/appsec/appsec-team/-/issues/426+

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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  • The when to get approval handbook section explains the workflow in more detail
• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

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