Change `model-transparency` access to `maintain`.

[mihaimaruseac]

Summary

Still debugging why we cannot have 2 teams in the repo, but also trying to fix permissions for the new team. At least this would guarantee that the new team has the right permissions (I think).

Release Note

NONE

Documentation

NONE

[github-actions[bot]]

:tropical_drink: preview on sigstore-github-sync/sigstore/github-prod

Pulumi report

``` Previewing update (sigstore/github-prod) View Live: https://app.pulumi.com/sigstore/sigstore-github-sync/github-prod/previews/361cac76-e943-4ecb-a0fa-24b6a89e1a50 @ Previewing update.... pulumi:pulumi:Stack: (same) [urn=urn:pulumi:github-prod::sigstore-github-sync::pulumi:pulumi:Stack::sigstore-github-sync-github-prod] @ Previewing update.... ~ github:index/teamRepository:TeamRepository: (update) [id=10329477:model-transparency] [urn=urn:pulumi:github-prod::sigstore-github-sync::github:index/teamRepository:TeamRepository::model-transparency-model-transparency] [provider=urn:pulumi:github-prod::sigstore-github-sync::pulumi:providers:github::default_6_2_1::c4864a06-f2c2-4a7a-b9b8-d9a955761310] ~ permission: "push" => "maintain" Resources: ~ 1 to update 591 unchanged ```

[cpanato]

why maintain, the push is not enough? asking this because all the settings should be done here.

[cpanato]

btw, fixed the model-transparency-codeowners not added to the repo, need to remove and readd, something weird happened

[mihaimaruseac]

Thank you for fixing. This was to test raising and lowering permissions.

The culprit was that in #454 I used the same team ID for both teams, so the latest one (with lower permissions) was what got applied (thank to @spencerschrock for debugging).

I'll send a PR to update documentation, but now this PR is no longer needed. Thank you

[mihaimaruseac]

Documentation update on #464