Moving core team docs from Code Contributor Program into Community Relations

Why is this change being made?

We need to redivide the responsibilities after the RIF, and that means that the code contributor program no longer exists on its own but has combined efforts with the Contributor Success team. The change moves the core team 1 level up, to the community relations level, also but makes it clear who the DRI is. I felt it was not useful to move it under Contributor Success, as it's a piece of Community Relations, which just happens to have Contributor Success as DRI today. We might scale in the future, so this sets us up for that.

@leetickett-gitlab I made the sentence of the DRI generic, as we could always decide to change. More ideal is if I could programmatically read it from the codeowners and add this in there Scratch that, I'll remove that section as it's clear from the right hand side who is the DRI.

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
  • 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
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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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