Update Windows Server 2019 VM image — end of mainstream support

An org-wide audit of the dotnet org found a reference to a Windows Server 2019 VM image (`1es-windows-2019`). Windows Server 2019 ended mainstream support in January 2024.

Part of [.NET OS Support Tracking](https://github.com/dotnet/core/issues/9638). See also: [dotnet/runtime#125690](https://github.com/dotnet/runtime/issues/125690), [dotnet/dotnet-buildtools-prereqs-docker#1605](https://github.com/dotnet/dotnet-buildtools-prereqs-docker/issues/1605).

## Tracking

- [ ] `1es-windows-2019` → `1es-windows-2022` (or newer)

## Details

https://github.com/dotnet/aspnetcore/blob/5b892736c24f973adbdc8a36542609dc403ed92d/.azure/pipelines/azure-pipelines-mirror-within-azdo.yml#L32

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