Remove `#include <bootstrap.h>`
Remove `#include <bootstrap.h>`

`bootstrap_port` is also declared in `mach/mach_init.h`, so this is
not necessary.

tjt263/tmux-MacOSX-pasteboard,ChrisJohnsen/tmux-MacOSX-pasteboard,lembacon/tmux-MacOSX-pasteboard,bradparks/tmux-MacOSX-pasteboard