MINOR: [C#] Bump Grpc.Tools from 2.56.2 to 2.57.0 in /csharp

Bumps [Grpc.Tools](https://github.com/grpc/grpc) from 2.56.2 to 2.57.0.
- [Release notes](https://github.com/grpc/grpc/releases)
- [Changelog](https://github.com/grpc/grpc/blob/master/doc/grpc_release_schedule.md)
- [Commits](https://github.com/grpc/grpc/commits)

---
updated-dependencies:
- dependency-name: Grpc.Tools
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

csharp/src/Apache.Arrow.Flight/Apache.Arrow.Flight.csproj

@@ -7,7 +7,7 @@
   <ItemGroup>
     <PackageReference Include="Google.Protobuf" Version="3.24.0" />
     <PackageReference Include="Grpc.Net.Client" Version="2.55.0" />
-    <PackageReference Include="Grpc.Tools" Version="2.56.2" PrivateAssets="All" />
+    <PackageReference Include="Grpc.Tools" Version="2.57.0" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">