Use .NET 8 for OneLocBuildSetup

[drewnoakes]

Fixes build failures during the localization stage on the insertion PR pipeline.

Microsoft Reviewers: Open in CodeFlow

[drewnoakes]

I tested this change in https://dev.azure.com/devdiv/DevDiv/_build/results?buildId=10876223&view=results on the rel/d17.13 branch, where it fixed the loc stage.

The problem it addresses:

2025-01-22T22:15:41.2490057Z ##[error]Error: The process 'C:\Program Files\dotnet\dotnet.exe' failed with exit code 1
2025-01-22T22:15:41.2495903Z ##[warning].NET 5 has some compatibility issues with older Nuget versions(<=5.7), so if you are using an older Nuget version(and not dotnet cli) to restore, then the dotnet cli commands (e.g. dotnet build) which rely on such restored packages might fail. To mitigate such error, you can either: (1) - Use dotnet cli to restore, (2) - Use Nuget version 5.8 to restore, (3) - Use global.json using an older sdk version(<=3) to build
2025-01-22T22:15:41.2497040Z Info: Azure Pipelines hosted agents have been updated and now contain .Net 5.x SDK/Runtime along with the older .Net Core version which are currently lts. Unless you have locked down a SDK version for your project(s), 5.x SDK might be picked up which might have breaking behavior as compared to previous versions. You can learn more about the breaking changes here: https://docs.microsoft.com/en-us/dotnet/core/tools/ and https://docs.microsoft.com/en-us/dotnet/core/compatibility/ . To learn about more such changes and troubleshoot, refer here: https://docs.microsoft.com/en-us/azure/devops/pipelines/tasks/build/dotnet-core-cli?view=azure-devops#troubleshooting
2025-01-22T22:15:41.2498014Z ##[error]Dotnet command failed with non-zero exit code on the following projects : [
  'D:\\a\\_work\\1\\s\\eng\\tools\\OneLocBuildSetup\\OneLocBuildSetup.csproj'
]
2025-01-22T22:15:41.2556724Z ##[section]Finishing: Run Setup