fix url for flybase xref
fix url for flybase xref

muffato/public-plugins,muffato/public-plugins,Ensembl/public-plugins,andrewyatz/public-plugins,muffato/public-plugins,andrewyatz/public-plugins,andrewyatz/public-plugins,andrewyatz/public-plugins,Ensembl/public-plugins,muffato/public-plugins,andrewyatz/public-plugins,Ensembl/public-plugins