ci: remove packaging for debian-buster

Since Debain buster distribution has reached its end-of-life building on
it is no longer supported.

Author: themilchenko

.github/workflows/packaging.yml

@@ -30,7 +30,6 @@ jobs:
       matrix:
         platform:
           - { os: 'debian', dist: 'stretch' }
-          - { os: 'debian', dist: 'buster' }
           - { os: 'debian', dist: 'bullseye' }
           - { os: 'el', dist: '7' }
           - { os: 'el', dist: '8' }