GESTrackEffect: Use gst_object_unref for the hash value destroyfunc
GESTrackEffect: Use gst_object_unref for the hash value destroyfunc

The values are GstObjects and it makes it easier to track in debug logs
when they are being unreffed.

pitivi/gst-editing-services,MathieuDuponchelle/PitiviGes,volodymyrrudyi/gst-editing-services,cfoch/ges,freesteph/gst-editing-services,ahmedammar/platform_external_gst_editing_services,MathieuDuponchelle/PitiviGes,cfoch/gst-editing-services,pitivi/gst-editing-services,luisbg/gst-editing-services,luisbg/gst-editing-services,MathieuDuponchelle/PitiviGes,volodymyrrudyi/gst-editing-services,cfoch/gst-editing-services,cfoch/ges,ahmedammar/platform_external_gst_editing_services,volodymyrrudyi/gst-editing-services,cfoch/ges,freesteph/gst-editing-services,pitivi/gst-editing-services,pitivi/gst-editing-services,MathieuDuponchelle/PitiviGes,cfoch/ges,cfoch/gst-editing-services,cfoch/gst-editing-services,freesteph/gst-editing-services