mpg123: removed unnecessary finalize function
mpg123: removed unnecessary finalize function

https://bugzilla.gnome.org/show_bug.cgi?id=687176

GrokImageCompression/gst-plugins-good,pexip/gst-plugins-good,StreamUtils/gst-plugins-good,pexip/gst-plugins-good,GrokImageCompression/gst-plugins-good,StreamUtils/gst-plugins-good,pexip/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,StreamUtils/gst-plugins-good,StreamUtils/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,GrokImageCompression/gst-plugins-good,GrokImageCompression/gst-plugins-good,GStreamer/gst-plugins-good