Bump NUnit from 4.2.0 to 4.2.1 in /src#580

dependabot[bot] merged 1 commit intomainVerifyTests/Verify.ImageSharp:mainfrom

dependabot/nuget/src/NUnit-4.2.1VerifyTests/Verify.ImageSharp:dependabot/nuget/src/NUnit-4.2.1Copy head branch name to clipboard