Remove obsolete reference to thrift

Followup to [RTBkit Discussion](https://groups.google.com/a/rtbkit.org/d/msg/discuss/-TxYCuDznvg/hhWmOeYGprsJ) / [platform-deps 130688887acb106866f1d64d558eeb8bbe2a7102](https://github.com/datacratic/platform-deps/commit/130688887acb106866f1d64d558eeb8bbe2a7102).

Related [rtbkit pull request](https://github.com/rtbkit/rtbkit/pull/91).

Perhaps there are other clients of platform-deps that should be similarly updated?