Change xUnit using directives to TUnit

Proprietary

Replace using Xunit; with using TUnit.Core; and using TUnit.Assertions;.

OpenRewrite.Recipes.CSharp.Migration.TUnit.FromXUnit.ChangeXUnitUsings

mod run . --recipe=OpenRewrite.Recipes.CSharp.Migration.TUnit.FromXUnit.ChangeXUnitUsings

Install it once, then run it on every repository under the current directory. New to the Moderne CLI? Set it up.