root-signing-staging: Do not use the new role yet

[jku]

This is a revert of half of #395.

'pulumi up' fails with this:

422 Role `write-with-bypass` is not available for the
sigstore/root-signing-staging repository.

I'm not sure why the custom role is not found. Let's revert this and I will investigate.

[github-actions]

🍹 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/7fd0b475-4508-4cc9-8150-653bf3074272

@ 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/teamMembership:TeamMembership: (delete)
    [id=6735686:asraa]
    [urn=urn:pulumi:github-prod::sigstore-github-sync::github:index/teamMembership:TeamMembership::asraa-timestamp-codeowners]
    role      : "member"
    teamId    : "6735686"
    username  : "asraa"
- github:index/teamMembership:TeamMembership: (delete)
    [id=6189278:asraa]
    [urn=urn:pulumi:github-prod::sigstore-github-sync::github:index/teamMembership:TeamMembership::asraa-architecture-doc-team]
    role      : "member"
    teamId    : "6189278"
    username  : "asraa"
- github:index/teamMembership:TeamMembership: (delete)
    [id=6840584:asraa]
    [urn=urn:pulumi:github-prod::sigstore-github-sync::github:index/teamMembership:TeamMembership::asraa-protobuf-specs-codeowners]
    role      : "member"
    teamId    : "6840584"
    username  : "asraa"
- github:index/teamMembership:TeamMembership: (delete)
    [id=6378909:asraa]
    [urn=urn:pulumi:github-prod::sigstore-github-sync::github:index/teamMembership:TeamMembership::asraa-tuf-root-signing-codeowners]
    role      : "member"
    teamId    : "6378909"
    username  : "asraa"
Resources:
- 4 to delete
573 unchanged

[jku]

The visible changes in pulumi preview are from #394 (which failed because of the issue that I'm working around in this PR)