DEX remove old pages

Why is this change being made?

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This MR adds the DEX Team Charter and does a major overhaul of the DEX handbook.

It removes the following pages:

URL	Reasoning
https://handbook.gitlab.com/handbook/marketing/digital-experience/website/core-web-vitals/	Old out dated page.
https://handbook.gitlab.com/handbook/marketing/digital-experience/website/launch-darkly/	Dupliactive of our A/B testing page, which also has launch darkly informaiton
https://handbook.gitlab.com/handbook/marketing/digital-experience/website/merge-requests/	This is common sense, and there is documentation through out GitLab on how to author and review merge request. We will be adding a DEX engineering sub section with accurate information.
https://handbook.gitlab.com/handbook/marketing/digital-experience/conversion/	Group page is not needed - revising group structure for FY25Q2
https://handbook.gitlab.com/handbook/marketing/digital-experience/smartling/	Smartling was never implemented
https://handbook.gitlab.com/handbook/marketing/digital-experience/writing-description-templates/	This information will be updated in next MR that adds DEX Engineering information

.**

• 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
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added, and the content is SAFE
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies
  • The when to get approval handbook section explains the workflow in more detail
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  • Team: For changes that affect your direct team, share in your group Slack channel
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    • For high-priority company-wide announcements work with the internal communications team to post the update in #company-fyi and align on a plan to circulate in additional channels like the "While You Were Iterating" Newsletter

Commits

• mild nuking of dex handbook

• remove old dex handbook things

• remove website portion from dex handbook?

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