Rebootstrap pipeline incorrectly truncated PSB artifacts version

[ellahathaway]

In dotnet/dotnet#514, the PSB artifacts version was set to 10.0.100-preview.5.25258.1. This is incorrect, as the artifacts version is 10.0.100-preview.5.25258.18. Looking at the logs from the rebootstrap pipeline run, the input to the script for updating the prop was correct, but the output was incorrect.

[MichaelSimons]

[Triage] This only occurred once. If this doesn't happen again, we should close it.

[MichaelSimons]

Fixed with https://dev.azure.com/dnceng/internal/_git/dotnet-release/pullrequest/51467