cpu-throttling-clock: free clock when finished

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9115>

subprojects/gst-plugins-bad/gst/transcode/gst-cpu-throttling-clock.c

@@ -169,6 +169,7 @@ gst_cpu_throttling_clock_dispose (GObject * object)
     gst_poll_free (self->priv->timer);
     self->priv->timer = NULL;
   }
+  g_clear_object (&self->priv->sclock);
 
   G_OBJECT_CLASS (parent_class)->dispose (object);
 }