I'm just blindly trusting this comment from Licaon_Kter lol:
https://gitlab.com/fdroid/fdroiddata/-/commit/67bfb5d0a87f6ee12137a39c095bda44187592b9#note_2139527294
The image was just copied from this image:
ic_launcher-playstore.png
So, from this version:
https://gitpull.it/source/libre-busto/browse/master/ic_launcher-playstore.png;8edbdcb07bba722d7f7639ff7cd9bbea90141ce0