Modifying list of approved operating systems to clarify Mint and PopOS support

Why is this change being made?

Clarifying that new hires shouldn't use Mint or PopOS as they aren't supported by SentinelOne or DriveStrike, and encouraging team members to migrate to officially supported distro.

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
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