[MINOR][DOC] Add missing session kind in documentation
[MINOR][DOC] Add missing session kind in documentation

## What changes were proposed in this pull request?

Add missing session kind in documentation.

## How was this patch tested?

no need to test

Author: Yishuang Lu <luystu@gmail.com>

Closes #227 from lys0716/dev.

meisam/incubator-livy,ajbozarth/incubator-livy,ajbozarth/incubator-livy,ajbozarth/incubator-livy,meisam/incubator-livy,ajbozarth/incubator-livy,ajbozarth/incubator-livy,meisam/incubator-livy,ajbozarth/incubator-livy,meisam/incubator-livy,meisam/incubator-livy,meisam/incubator-livy