Reenable skipped IIS tests

[ajaybhargavb]

More context here, #20053 (comment)

Blocked on dotnet/runtime#34093

[javiercn]

@ajaybhargavb I believe this is MVC, isn't it? Moved to next sprint planning. Label this issue as needed please.

[ajaybhargavb]

This is area-servers. I've modified it.

[BrennanConroy]

Fixed via #20417