Update NuGet package version of SIL.Chorus.Mercurial

[rmunn]

The SIL.Chorus.Mercurial package was just updated to version 6.5.1.29 to fix an omission in the Linux packaging of Mercurial 6. That omission didn't cause any bugs that we can currently see, but is blocking #631 until that new version can be included. But there's no reason to delay pulling down the new bugfix package until #631 is complete; let's pull down that bugfix right now.