getdeps: upgrade zstd from 1.3.8 -> 1.4.4
getdeps: upgrade zstd from 1.3.8 -> 1.4.4

Summary:
I'm doing this mostly so that we can avoid using git
to fetch the sources.

Reviewed By: chadaustin

Differential Revision: D21508201

fbshipit-source-id: 54d4635d8938659bea962e90bd829d237f1ed221

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly