youtube: remove unused variable
youtube: remove unused variable

grl-youtube.c:591:10: warning: unused variable ‘id’ [-Wunused-variable]
  gchar *id;
         ^~

https://bugzilla.gnome.org/show_bug.cgi?id=770806

jasuarez/grilo-plugins,GNOME/grilo-plugins,GNOME/grilo-plugins,jasuarez/grilo-plugins,MikePetullo/grilo-plugins,grilofw/grilo-plugins,MikePetullo/grilo-plugins,MikePetullo/grilo-plugins,grilofw/grilo-plugins