[GRASS-git] [OSGeo/grass] ef2b98: CI: Remove Ubuntu 18.04 check (#2324)

[Vaclav Petras]

  Branch: refs/heads/releasebranch_8_0
  Home:   https://github.com/OSGeo/grass
  Commit: ef2b983f7ebec33710f52305d5460a6bbd091556
      https://github.com/OSGeo/grass/commit/ef2b983f7ebec33710f52305d5460a6bbd091556
  Author: Vaclav Petras <wenzeslaus at gmail.com>
  Date:   2022-04-26 (Tue, 26 Apr 2022)

  Changed paths:
    M .github/workflows/ubuntu.yml

  Log Message:
  -----------
  CI: Remove Ubuntu 18.04 check (#2324)

We don't support Ubuntu 18.04 for 8.0 anymore.