Static analysis: remove trailing commas

[ajcvickers]

Part of #26805

[sharwell]

This change has the negative side effect of reducing the effectiveness of git blame and increasing code churn. See also SA1413 Use trailing comma in multi-line initializers and DotNetAnalyzers/StyleCopAnalyzers#2884. I would strongly encourage reporting a bug to the authors of the tool that led to this analysis warning with a request that the rule be eliminated or corrected.

[ajcvickers]

At this point, the cleanup is just about being consistent. We decided this so long ago that I don't remember much about the discussion. It's easy to go the other way if people on the team feel like we should.

/cc @dotnet/efteam