Remove XunitRunnerVisualStudioVersion from Version.props after Arcade update

[pranavkm]

To get tests running, AspNetCore's versions.props file explicitly specifies a version for XunitRunnerVisualStudio:

https://github.com/dotnet/aspnetcore/pull/24685/files#diff-8b8f08ffbf7b863fb3700c1718eeb4cbR282

Once dotnet/arcade#5908 is merged and an Arcade update is available, this can be removed.

[dougbu]

@pranavkm why remove the property when it matches what Arcade provides and keeps all xUnit properties together❔ Arcade doesn't provide versions for many of the xUnit packages we use. And, we have a history of staying ahead of Arcade versions (admittedly, that's not the case for the few xUnit versions Arcade has at the moment).

[dougbu]

/ping @pranavkm

[wtgodbe]

/ping @pranavkm

[pranavkm]

I think @dougbu asked me to file this issue - see #24685 (comment).

[dougbu]

Changed my mind on the value