fix minio-dotnet build

[halkyon]

While this fixes the docker build, it doesn't seem to pass the tests:

(1/1) Running minio-dotnet tests ... ./run.sh: line 26:  1382 Aborted                 (core dumped) /mint/run/core/minio-dotnet/out/Minio.Functional.Tests >> "$output_log_file" 2> "$error_log_file"
FAILED in 2 seconds
{
  "name": "minio-dotnet : MakeBucket_Test1",
  "function": "Task MakeBucketAsync(string bucketName, string location = 'us-east-1', CancellationToken cancellationToken = default(CancellationToken))",
  "args": {
    "bucketName": "minio-dotnet-example-ut0qtw5ieu0ni4ofg812kpgswjgsol9eqk5fqghlzh451qge1n",
    "region": "us-east-1"
  },
  "duration": 0,
  "status": "FAIL",
  "alert": "MinIO API responded with message=Bucket name cannot be greater than 63 characters.",
  "message": "minio-dotnet-example-ut0qtw5ieu0ni4ofg812kpgswjgsol9eqk5fqghlzh451qge1n: Minio.Exceptions.InvalidBucketNameException: MinIO API responded with message=Bucket name cannot be greater than 63 characters.\n   at Minio.utils.ValidateBucketName(String bucketName) in /mint/run/core/minio-dotnet/temp/Minio/Helper/utils.cs:line 60\n   at Minio.BucketArgs`1.Validate() in /mint/run/core/minio-dotnet/temp/Minio/DataModel/BucketArgs.cs:line 58\n   at Minio.MinioClient.MakeBucketAsync(MakeBucketArgs args, CancellationToken cancellationToken) in /mint/run/core/minio-dotnet/temp/Minio/ApiEndpoints/BucketOperations.cs:line 128\n   at Minio.Functional.Tests.FunctionalTest.MakeBucket_Test1(MinioClient minio) in /mint/run/core/minio-dotnet/temp/Minio.Functional.Tests/FunctionalTest.cs:line 293"
}

I'm not sure why though.