Remove Buster testing

Debian buster is not supported for a while now in OSA, so we should
remove it from testing platfrom.

Change-Id: I717a1e3593c161f179dc8fb63d5b85677f606956

.zuul.yaml

@@ -1,11 +1,5 @@
 ---
 
-- job:
-    name: tox-molecule-buster
-    parent: tox-molecule
-    vars:
-      tox_envlist: molecule-buster
-
 - job:
     name: tox-molecule-bookworm
     parent: tox-molecule
@@ -28,14 +22,12 @@
     check:
       jobs:
         - tox-linters
-        - tox-molecule-buster
         - tox-molecule-bookworm
         - tox-molecule-jammy
         - tox-molecule-stream9
     gate:
       jobs:
         - tox-linters
-        - tox-molecule-buster
         - tox-molecule-bookworm
         - tox-molecule-jammy
         - tox-molecule-stream9

tox.ini

@@ -54,15 +54,6 @@ commands =
 setenv =
     {[testenv]setenv}
 
-[testenv:molecule-buster]
-deps =
-    {[molecule]deps}
-commands =
-    {[molecule]commands}
-setenv =
-    {[molecule]setenv}
-    docker_image_tag=debian-systemd:buster
-
 [testenv:molecule-bookworm]
 deps =
     {[molecule]deps}
@@ -81,6 +72,7 @@ setenv =
     {[molecule]setenv}
     docker_image_tag=ubuntu-systemd:jammy
 
+
 [testenv:molecule-stream9]
 deps =
     {[molecule]deps}