gdb/infcmd: remove the unused parameter 'args' in 'attach_post_wait'

gdb/infcmd: remove the unused parameter 'args' in 'attach_post_wait'

The 'arg' parameter of 'attach_post_wait' is unused.  Remove it.

gdb/ChangeLog:
2021-04-22  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* infcmd.c (attach_post_wait): Remove the unused parameter 'args'.
	Update the references below.
	(struct attach_command_continuation_args)
	(attach_command_continuation)
	(attach_command_continuation_free_args)
	(attach_command)
	(notice_new_inferior): Update to remove the reference to 'args'.