Update C# E2E project's test package versions (#21975)
### Description
<!-- Describe your changes. -->
Update C# test package dependencies to match #21913
This csproj isn't included in the main sln and was overlooked. We need
the newer xunit version for Assert.Fail which is used in shared unit
test source that is included here as well.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Fix CI failure
