Update segmentation_dataset.py
Update segmentation_dataset.py

Update ADE20K dataset info.
tombstone/models,alexgorban/models,tombstone/models,alexgorban/models,derekjchow/models,tombstone/models,cshallue/models,cshallue/models,cshallue/models,derekjchow/models,cshallue/models,derekjchow/models,tombstone/models,derekjchow/models,derekjchow/models,alexgorban/models,alexgorban/models,tombstone/models,alexgorban/models,cshallue/models,tombstone/models