Remove jschelpers and privatedata

Summary: JSI doesn't use any of this.

Reviewed By: RSNara

Differential Revision: D10229167

fbshipit-source-id: 9eaa288a1d62bafb3ff0626f9f8430e699fdad4a

Author: mhorowitz

ReactCommon/cxxreact/BUCK

@@ -147,6 +147,5 @@ rn_xplat_cxx_library(
         react_native_xplat_target("microprofiler:microprofiler"),
         "xplat//folly:optional",
         "xplat//third-party/glog:glog",
-        react_native_xplat_target("privatedata:privatedata"),
     ],
 )