Remove migrated all-orgs artifact-feed PAT

[missymessa]

Summary

Removes the managed dn-bot-all-orgs-artifact-feeds-rw PAT from the EngKeyVault secret-manager manifest now that all confirmed active consumers have migrated.

Validation

• Arcade Build Promotion uses keyless Entra publishing on main; real post-merge publishing succeeded in both dnceng and DevDiv.
• dotnet-interactive NPM publishing migrated to npmAuthenticate@0; post-merge build 3038004 published successfully.
• release/6.0 direct PAT injection was removed by [release/6.0] Remove artifact-feed PAT from asset publishing #17244; post-merge build 3039325 successfully completed NuGetAuthenticate@1 and Publish Build Assets, pushing BAR build 325726.
• Maintained Arcade branches have no remaining direct authentication use of this PAT. Remaining release/9.0 and release/10.0 occurrences are log-redaction placeholders only.

After this merges, remove the secret from the Key Vault-backed AzureDevOps-Artifact-Feeds-Pats variable-group sync list, then retire the Key Vault secret.

Related: https://dnceng.visualstudio.com/internal/_workitems/edit/10145

[Copilot]

Pull request overview

This PR updates Arcade’s EngKeyVault secret-manager manifest to remove the managed Azure DevOps PAT dn-bot-all-orgs-artifact-feeds-rw now that known active consumers have migrated away from it.

Changes:

• Removes the dn-bot-all-orgs-artifact-feeds-rw azure-devops-access-token secret entry from the EngKeyVault manifest.
• Eliminates the associated #AzureDevOps-Artifact-Feeds-Pats section header in that manifest.

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[missymessa]

Validation build 1540241 passed every build and local test leg. The only failure was the Helix monitor timing out after 85 minutes with two jobs still waiting on �windows.11.amd64.client.open�; submission warned that the queue's estimated wait was 45-46 minutes over the 30-minute SLA. This is unrelated to the vault-manifest change. I requeued the PR validation as build 1540415: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1540415