Update donate.tpo gift images for YEC 2023

hi @kez, could you please update the donate.tpo page with these images so that they're ready for the Oct 16th launch? thank you! :)

• yec-tee-web.png - should replace the "Once $75" t-shirt
• yec-combo-tee-web - should replace the "Once $125" combo

Also tagging @mattlav here because I think he has a few changes for options provided on both of these sections!