Missing symbols for the Microsoft.Extensions.ApiDescription.Client package

[dougbu]

Symbol check fails consistently for the assemblies in this package.

See https://dnceng.visualstudio.com/internal/_releaseProgress?_a=release-environment-logs&releaseId=7988&environmentId=22139 Details:

2019-05-23T22:21:37.0497796Z Validating Microsoft.Extensions.ApiDescription.Client.0.3.0-preview6-19272-03.nupkg 
2019-05-23T22:21:38.8856205Z 	 Checking file E:\A\_work\r1\a\checkSymbols\3dbc120b-8427-478b-90c3-3e27525d6ced\tasks\net461\Microsoft.Extensions.ApiDescription.Tasks.dll ... No symbols found on MSDL or SymWeb!
2019-05-23T22:21:40.7486530Z 	 Checking file E:\A\_work\r1\a\checkSymbols\3dbc120b-8427-478b-90c3-3e27525d6ced\tasks\netstandard2.0\Microsoft.Extensions.ApiDescription.Tasks.dll ... No symbols found on MSDL or SymWeb!
2019-05-23T22:21:40.8294325Z CheckSymbolsAvailable : Missing symbols for 2 modules in the package