remove red-herring CMake file
remove red-herring CMake file

Summary:
This is a leftover CMake file from when we first open sourced
FBOSS. The actual one is in fboss/github/.

Differential Revision: D4569048

fbshipit-source-id: 84c64da83d8e57b6a2bbf39ffa85dabb3f65e0eb

peterlei/fboss,peterlei/fboss,peterlei/fboss,peterlei/fboss