MINOR: [C#] Bump Grpc.Tools from 2.71.0 to 2.76.0#75

dependabot[bot] wants to merge 1 commit into5588-Better-support-for-building-UnionArraysQuietCraftsmanship/arrow:5588-Better-support-for-building-UnionArraysfrom

dependabot/nuget/csharp/src/Apache.Arrow.Flight.Sql/Grpc.Tools-2.76.0QuietCraftsmanship/arrow:dependabot/nuget/csharp/src/Apache.Arrow.Flight.Sql/Grpc.Tools-2.76.0Copy head branch name to clipboard