[OpenSIPS-Devel] [OpenSIPS/opensips] a90ecc: github: remove Xenial builds

[Răzvan Crainea]

  Branch: refs/heads/master
  Home:   https://github.com/OpenSIPS/opensips
  Commit: a90eccf9cd59154577cb5b2d94fa9261b9bb657e
      https://github.com/OpenSIPS/opensips/commit/a90eccf9cd59154577cb5b2d94fa9261b9bb657e
  Author: Razvan Crainea <razvan at opensips.org>
  Date:   2021-05-10 (Mon, 10 May 2021)

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

  Log Message:
  -----------
  github: remove Xenial builds

Xenial had become unmaintained on 30th of April 2021, and on 4th of May
2021 GitHub Actions deprecated it: actions/virtual-environments#3302