gstutils: remove obsolete Fixme comment
gstutils: remove obsolete Fixme comment

gst_pad_link_filtered() is very long gone and current
gst_element_link_pads_filtered() doesn't apply to this Fixme comment.

StreamUtils/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,mparis/gstreamer,centricular/gstreamer,mparis/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,mparis/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,krichter722/gstreamer,centricular/gstreamer,jpxiong/gstreamer