Build uses unpublished Chorus package

[rmunn]

Directory.Build.props currently (2024-12-03) has <ChorusVersion>6.0.0-beta0059</ChorusVersion>, but https://www.nuget.org/packages/SIL.Chorus.ChorusMerge/6.0.0-beta0059 says that beta0059 was unlisted by the package owner. So I currently cannot get flexbridge to compile.

This issue is just to remind us to bump the ChorusVersion to beta0060 or higher once a new Chorus build is made, or once beta0059's problems are fixed and it's un-unlisted (relisted?).