wallpapers/potd: remove unsplash provider
https://source.unsplash.com has been deprecated and doesn't work anymore. To use Unslash in needs a developer access key and use the https://api.unsplash.com BUG: 471526 FIXED-IN: 5.27.7
https://source.unsplash.com has been deprecated and doesn't work anymore. To use Unslash in needs a developer access key and use the https://api.unsplash.com BUG: 471526 FIXED-IN: 5.27.7
mentioned in commit 5eff4797