MINOR: [C#] Bump Grpc.Tools from 2.42.0 to 2.56.2 in /csharp (#36727)

Bumps [Grpc.Tools](https://github.com/grpc/grpc) from 2.42.0 to 2.56.2.
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Authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Signed-off-by: Jacob Wujciak-Jens <jacob@wujciak.de>

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

@@ -7,7 +7,7 @@
  <ItemGroup>
  <PackageReference Include="Google.Protobuf" Version="3.19.3" />
  <PackageReference Include="Grpc.Net.Client" Version="2.52.0" />
- <PackageReference Include="Grpc.Tools" Version="2.42.0" PrivateAssets="All" />
+ <PackageReference Include="Grpc.Tools" Version="2.56.2" PrivateAssets="All" />
  </ItemGroup>
 
  <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">