Update AutoRest C# version (#16390)
Update AutoRest C# version (#16390)

Update AutoRest C# version to 1.0.0-alpha.20201028.2
jackmagic313/azure-sdk-for-net,AsrOneSdk/azure-sdk-for-net,ayeletshpigelman/azure-sdk-for-net,ayeletshpigelman/azure-sdk-for-net,jackmagic313/azure-sdk-for-net,yugangw-msft/azure-sdk-for-net,brjohnstmsft/azure-sdk-for-net,ayeletshpigelman/azure-sdk-for-net,brjohnstmsft/azure-sdk-for-net,brjohnstmsft/azure-sdk-for-net,AsrOneSdk/azure-sdk-for-net,yugangw-msft/azure-sdk-for-net,jackmagic313/azure-sdk-for-net,jackmagic313/azure-sdk-for-net,AsrOneSdk/azure-sdk-for-net,yugangw-msft/azure-sdk-for-net,AsrOneSdk/azure-sdk-for-net,brjohnstmsft/azure-sdk-for-net,ayeletshpigelman/azure-sdk-for-net,brjohnstmsft/azure-sdk-for-net,jackmagic313/azure-sdk-for-net