bt_ctf_event_set_clock_value() does not need a clock class

bt_ctf_event_set_clock_value() does not need a clock class

Since a clock value has a clock class member, and you can
get it with bt_ctf_clock_value_get_class(), it's redundant
to specify both the clock class and the clock value when
you call bt_ctf_event_set_clock_value().

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>