Remove extra -I for python bindings

Same fix as for lttng-tools commit f7cbc765ad2526667f1f20b3a89c596b3422ac34

Signed-off-by: Yannick Brosseau <yannick.brosseau@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>