Remove lfs dependencies

[hanefi]

We no longer use lfs to store large datasets in this repo.

The .gitattributes files need to be revised to remove these dependencies. We may also need to supply a list of steps to remove existing git hooks that lfs created.

I found 2 places that needs revision but we may need to investigate more on this https://github.com/citusdata/postgresql-topn/blob/66e2eeed2417d159135b638f83846b1bbdf7aa33/data/.gitattributes#L1 https://github.com/citusdata/postgresql-topn/blob/66e2eeed2417d159135b638f83846b1bbdf7aa33/.gitattributes#L2