Cleanup: common/assert.c: remove useless calls

Cleanup: common/assert.c: remove useless calls

  CID 1401190 (#1 of 1): Useless call (USELESS_CALL)
  side_effect_free: Calling bt_common_color_bold() is only useful for
  its return value, which is ignored.

  side_effect_free: Calling bt_common_color_fg_red() is only useful for
  its return value, which is ignored.

Reported-by: Coverity (1401190) Useless call
Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Ia25823f44c24997782ccc209c48d5b28a45a98f4
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1287
Reviewed-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>