Fix symbol upload

[epananth]

To double check:

• The right tests are in and and the right validation has happened. Guidance: https://github.com/dotnet/core-eng/tree/master/Documentation/Validation

Issue -> https://github.com/dotnet/core-eng/issues/12893

Test build -> https://dnceng.visualstudio.com/internal/_build/results?buildId=1100201&view=logs&j=ba23343f-f710-5af9-782d-5bd26b102304&t=6e277ba4-1c1e-552d-b96f-db0aeb4be20a

[ViktorHofer]

A test would be useful to protect this from regressing again.

[epananth]

I am adding some more test as a part of publishing here-> #7190 I will think of more test to cover symbol publishing as part of this exercise.

[missymessa]

LGTM

[epananth]

verified it against general-testing-internal channel https://dnceng.visualstudio.com/internal/_build/results?buildId=1100514&view=results and @hoyosjs confirmed he can download the files.

Symweb needs corpnet to download the files.

[markwilkie]

thanks @epananth !