Dead Code: wangle/concurrent/ThreadedExecutor.h
Dead Code: wangle/concurrent/ThreadedExecutor.h

Summary:
[Wangle] Dead Code: `wangle/concurrent/ThreadedExecutor.h`.

It was just a shim around `folly/executors/ThreadedExecutor.h` but the shim is no longer required.

Reviewed By: Orvid

Differential Revision: D6098058

fbshipit-source-id: ca054a2c490e8da81b8e6d5d7d2921383c4fceb4

facebook/wangle,facebook/wangle,facebook/wangle