Add Talk invert filters for group subjects (#5990)
Add Talk invert filters for group subjects (#5990)

#5985 has broken the invert filter for the classifier on projects like Plankton Portal. This redoes the CSS change, but scopes it only to group subjects (`subject-viewer--layout-grid4`.) Images in the classifier shouldn't be accidentally styled by this change, like they were in the previous PR.
zooniverse/Panoptes-Front-End