Update target platforms for debs (#588)

* Bionic is in ESM and does not package importlib-metadata
* Buster does not package importlib-metadata
* Stretch has Python 3.5 and hasn't been support for a long time now
* Bookworm is the current "stable" Debian

publish-python.yaml

@@ -8,9 +8,7 @@ artifacts:
         config:
           repository: dirk-thomas/colcon
           distributions:
-            - ubuntu:bionic
             - ubuntu:focal
             - ubuntu:jammy
-            - debian:stretch
-            - debian:buster
             - debian:bullseye
+            - debian:bookworm

stdeb.cfg

@@ -3,5 +3,5 @@ No-Python2:
 Depends3: python3-distlib, python3-empy, python3-packaging, python3-pytest, python3-setuptools
 Recommends3: python3-pytest-cov
 Suggests3: python3-pytest-repeat, python3-pytest-rerunfailures
-Suite: bionic focal jammy stretch buster bullseye
+Suite: focal jammy bullseye bookworm
 X-Python3-Version: >= 3.6