Bump xunit.runner.visualstudio from 3.1.5 to 4.0.0 - #89

C:\Users\runneradmin\.nuget\packages\mockly\1.7.0\buildTransitive\Mockly.targets(31,5): warning MSB3026: Could not copy "C:\Users\runneradmin\.nuget\packages\mockly\1.7.0\buildTransitive\..\skills\mockly\SKILL.md" to "D:\a\fluentassertions.mockly\fluentassertions.mockly\.agents\skills\mockly\SKILL.md". Beginning retry 1 in 1000ms. The process cannot access the file 'D:\a\fluentassertions.mockly\fluentassertions.mockly\.agents\skills\mockly\SKILL.md' because it is being used by another process. [D:\a\fluentassertions.mockly\fluentassertions.mockly\FluentAssertions.Mockly.v8\FluentAssertions.Mockly.v8.csproj::TargetFramework=net472]