gst-libs/gst/interfaces/propertyprobe.c: Fix wrong macro usage; it's G_OBJECT_GET_CLA...

gst-libs/gst/interfaces/propertyprobe.c: Fix wrong macro usage; it's G_OBJECT_GET_CLASS(obj) or ot G_OBJECT_CLASS(obj...

Original commit message from CVS:
Reviewed by: Tim-Philipp Müller  <tim at centricular dot net>
* gst-libs/gst/interfaces/propertyprobe.c:
(gst_property_probe_probe_property_name),
(gst_property_probe_needs_probe_name),
(gst_property_probe_get_values_name),
(gst_property_probe_probe_and_get_values_name):
Fix wrong macro usage; it's G_OBJECT_GET_CLASS(obj) or
G_OBJECT_CLASS(klass), not G_OBJECT_CLASS(obj). (#316571)