player: fix gtk-doc documentation format
player: fix gtk-doc documentation format

guiseco/gst-player,JimmyOhn/gst-player,amorenoc/gst-player,sdroege/gst-player,amorenoc/gst-player,codomania/gst-player,sdroege/gst-player,codomania/gst-player,jabiers/gst-player,shakin/gst-player,jabiers/gst-player,shakin/gst-player,JimmyOhn/gst-player,codomania/gst-player,amorenoc/gst-player,amorenoc/gst-player,JimmyOhn/gst-player,sdroege/gst-player,JimmyOhn/gst-player,sdroege/gst-player,codomania/gst-player,justinjoy/gst-player,JimmyOhn/gst-player,jabiers/gst-player,justinjoy/gst-player,guiseco/gst-player,guiseco/gst-player,amorenoc/gst-player,codomania/gst-player,justinjoy/gst-player,sdroege/gst-player,shakin/gst-player