pybind/mgr/pg_autoscaler: fix progress event of the autoscaler

pybind/mgr/pg_autoscaler: fix progress event of the autoscaler

Problem:
We are comparing the wrong value when determining whether the Autoscaler event should be completed or not,
we compared pool_data["pg_num"] == pool_data["pg_num_target"] which will always return true since pool_data["pg_num_target"]
is not actual the target pg we are trying to scale towards, but rather the previous calculated value
that we
are expected to already reached based on previous values.

Solution:
Use the correct value which is comparing pool_data[‘pg_num’] == ev.pg_num_target.

Fixes: https://tracker.ceph.com/issues/72857
Signed-off-by: Kamoltat Sirivadhna <ksirivad@redhat.com>