Upgrade from `heroku/buildpacks:20` to `heroku/builder:20`
There is a detailed description of the current situation with the
heroku/builderpacks and heroku:builder images at
#73 (comment 1793611360)
tl;dr: in a couple weeks time (unknown exact date) the deprecation of
the heroku/buildpacks:20 images will raise an error instead of just a
warning.
This may actually be a breaking change for some user - arguably though
the better outcome as broken pipelines for all users because of the
raised error of heroku/buildpacks:20.
To quote Ed Morely, Heroku Team Member (from the aforementioned issue):
There would be some small differences in buildpack behaviour, since the next-gen buildpacks have intentionally dropped support for some lesser used legacy features - however, for many languages/apps it would be mostly a drop-in replacement.
Both images have the same base image (Ubuntu 20.04) which also minimizes the impact.