Bump Pipeline Timeout for Regen Preview

The 60 min timeout on regen preview runs is leading to the job being canceled. We should consider bumping this to 90 minutes. https://github.com/microsoft/typespec/blob/main/packages/http-client-csharp/eng/pipeline/publish.yml#L191

example run:
https://dev.azure.com/azure-sdk/internal/_build/results?buildId=6069133&view=results