[Swan-commit] Changes to ref refs/heads/main

[Andrew Cagney]

New commits:
commit bf377ded9d8659e63be70415506acf5f9ba9104e
Author: Andrew Cagney <cagney at gnu.org>
Date:   Thu Dec 28 11:23:13 2023 -0500

    building: drop Ubuntu 18.04 LTS (Bionic Beaver)
    
    expired in April 2023; fix #1462