Fix photos plugin tests by excluding pandoc_reader
Fix photos plugin tests by excluding pandoc_reader

This plugin reader caused urlescaping of curly braces,
which broke tests "test_filename_article_body" & "test_photo_article_body"

mortada/pelican-plugins,mortada/pelican-plugins,rlaboiss/pelican-plugins,mikitex70/pelican-plugins,talha131/pelican-plugins,talha131/pelican-plugins,MarkusH/pelican-plugins,xsteadfastx/pelican-plugins,xsteadfastx/pelican-plugins,rlaboiss/pelican-plugins,mikitex70/pelican-plugins,talha131/pelican-plugins,MarkusH/pelican-plugins,rlaboiss/pelican-plugins,mikitex70/pelican-plugins,mortada/pelican-plugins,MarkusH/pelican-plugins,mikitex70/pelican-plugins,MarkusH/pelican-plugins,xsteadfastx/pelican-plugins,mortada/pelican-plugins,MarkusH/pelican-plugins,talha131/pelican-plugins,rlaboiss/pelican-plugins,xsteadfastx/pelican-plugins,talha131/pelican-plugins,mortada/pelican-plugins