[BUG] Bare-metal portal preview requests provisionedClusterInstances API 2026-04-01-preview — not supported in eastus

[jeffjfield]

Following aks-bare-metal-create-cluster-portal (which directs deployment into East US), the portal wizard fails with:
No registered resource provider found for location 'eastus' and API version '2026-04-01-preview' for type 'provisionedClusterInstances'. The supported api-versions are '2023-11-15-preview, 2024-01-01'...

The portal blade is pinned to 2026-04-01-preview, but the Microsoft.HybridContainerService RP in eastus only serves up to 2024-01-01