They still have the bug bounty for the Pixel devices. I don't know they ever had one for the open source Android OS (AOSP), but a bug in AOSP would be likely to effect a Pixel device. The bug bounty that is getting removed is one that google offered for certain very popular apps in the play store. I also see that have bug bounty's for some of the main Google android apps.

https://bughunters.google.com/about/rules/android-friends/61... https://bughunters.google.com/report/targets/290590452