TST: Fix thumbnailer
TST: Fix thumbnailer

Due to change in pillow aspect rounding:
* https://github.com/python-pillow/Pillow/pull/4256

MarkusH/pelican-plugins,MarkusH/pelican-plugins,mortada/pelican-plugins,mortada/pelican-plugins,mortada/pelican-plugins,mortada/pelican-plugins,MarkusH/pelican-plugins,MarkusH/pelican-plugins,mikitex70/pelican-plugins,mikitex70/pelican-plugins,mikitex70/pelican-plugins,mikitex70/pelican-plugins,mortada/pelican-plugins,MarkusH/pelican-plugins