Xcode clang seems unhappy with both FileExplorerLib.h and
Protocol/FileExplorer.h both defining CHOOSE_HANDLER, now
remove the definition in FileExplorerLib.h.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Andrew Fish <afish@apple.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>