Tweak reviewers/maintainers to release-tools engineering project

Why is this change being made?

We are enabling danger-review (see gitlab-org/release-tools!2728 (merged)) on https://gitlab.com/gitlab-org/release-tools/ which also include Reviewer Roulette functionality.

With that we also need to update the list of reviewers/maintainers on release-tools project so Reviewer Roulette can use it.

This MR does.

Contributes to gitlab-com/gl-infra/delivery#19780 (closed).

But how?

• List of maintainers take from https://gitlab.com/groups/gitlab-org/delivery/-/group_members?with_inherited_permissions=exclude which is member of https://gitlab.com/gitlab-org/release-tools/-/project_members?with_inherited_permissions=exclude&tab=groups
• All engineers (backend and SREs) become maintainer
• Management is skipped
• @splattael is added a (currently sole) reviewer
• @jarv is removed as a reviewer because he is no longer active on this project (verified via Slack)

Screenshots

Before	After

Author and Reviewer Checklist

Please verify the check list and ensure to tick them off before the MR is merged.

• 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
• For transparency, share this MR with the audience that will be impacted.
  • Team: For changes that affect your direct team, share in your group Slack channel
  • Department: If the update affects your department, share the MR in your department Slack channel
  • Company: If the update affects all (or the majority of) GitLab team members, post an update in #whats-happening-at-gitlab linking to this MR
    • 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

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