new yarn versions are missing

[lizthegrey]

Describe the bug
v220 was just released today, and should have Yarn 4.0.0-rc.50 (released 3 weeks ago) but instead only has through Yarn 4.0.0-rc.48

To Reproduce

  "engines": {
    "node": "20.6.1",
    "yarn": "4.0.0-rc.50"
  },

       !     No matching version found for Yarn: 4.0.0-rc.50
       
       Heroku supports most versions of Yarn published on npm, however you have
       specified a version in package.json (4.0.0-rc.50) that does not correspond
       to any published version of Yarn. You can see a list of all published
       versions of Yarn with the following command:

[colincasey]

The Yarn versions used by this buildpack are sourced from our Cloud Native Node.js Buildpacks. Once heroku/buildpacks-nodejs#647 is fixed, the new Yarn versions will arrive.

[colincasey]

Fixed in release v221 (#1139).