DEV: Remove warnings on console (PR #14608)

We don’t use oxipng from the image_optim gem and rake tasks complained that constants have already been initialized.


The standard question in case of ||= changes: do we know why this file is loaded more than once? :slightly_smiling_face:

Unfortunately not. I’ve seen those warnings only in production. I didn’t want to invest too much time in figuring it out what’s different in production. Maybe a plugin? :man_shrugging: