MINOR: [C#] Bump Microsoft.NET.Test.Sdk from 17.12.0 to 18.0.0#69

dependabot[bot] wants to merge 1 commit intoupstreamsmellman/debian-apache-arrow:upstreamfrom

dependabot/nuget/csharp/test/Apache.Arrow.Compression.Tests/multi-ccbe046fc6smellman/debian-apache-arrow:dependabot/nuget/csharp/test/Apache.Arrow.Compression.Tests/multi-ccbe046fc6Copy head branch name to clipboard