vips no longer needs custom buildpack to be installed

[jrochkind]

Newlywords/heroku-buildpack-vips#36

We can now list libvips-tools in Aptfile to succesfully get vips command-line.

To get vips to include OpenJPEG/jp2 support, which we need for #2254 -- we need to go to heroku-22. It just works on heroku-22, but not heroku-20, not sure why.

This is true either with custom buildpack approach, or with new just Aptifle approach. We get OpenJPEG with heroku-22, not heroku-20.

So as part of this change, we should move to heroku-22 -- and #2090 is really a pre-requisite, I will probably prioritize doing that first.

Cc @eddierubeiz

[jrochkind]

Actually, nope, maybe not ready for prime-time, what we're doing is fine for now, and we don't get much advantage from trying to switch.

Newlywords/heroku-buildpack-vips#36 (comment)

We DO need to switch to heroku-22 to get the vips install to have OpenJPEG support though.