Stop es-2.x branch
Stop es-2.x branch

The code moved to elasticsearch repository. See https://github.com/elastic/elasticsearch/pull/14902

So we can close the `es-2.x` branch.

ggchangan/elasticsearch-mapper-attachments,ggchangan/elasticsearch-mapper-attachments,elastic/elasticsearch-mapper-attachments,ggchangan/elasticsearch-mapper-attachments,elastic/elasticsearch-mapper-attachments,elastic/elasticsearch-mapper-attachments