[Ada] Remove unused parameter from __gnat_kill

[Ada] Remove unused parameter from __gnat_kill

Remove close parameter from __gnat_kill because it is not used in
implementation.

gcc/ada/

	* adaint.c (__gnat_kill): Remove close parameter.
	(__gnat_killprocesstree): Do not provide close parameter on call
	to __gnat_kill.
	* libgnat/g-expect.adb (Kill): Remove Close parameter.
	(Close): Do not provide Close parameter on call to Kill.
	(Send_Signal): Do not provide Close parameter on call to Kill.
	* libgnat/s-os_lib.adb (Kill): Do not provide close parameter on
	call to __gnat_kill.