Draft: whitelist: drop v2020 and v2022 because EOL

Whitelists cleaning:

• buster is no longer tracked, and currently only debian/bullseye-backports is used.
• drop whitelists for v2020 since it's EOL
• drop whitelists for v2022 since it's EOL

bin/packaging-check-invariants

@@ -581,7 +581,8 @@ class InvariantChecker:
                 ignore_list = dict(
                     ignore_list, **LINUX_FAILED_PIPELINE_BRANCH_IGNORELIST
                 )
-            ignore_reason = ignore_list.get(branch.name)
+            if ignore_list is not None:
+                ignore_reason = ignore_list.get(branch.name)
             if ignore_reason:
                 logging.info(
                     f"{package.name}: Pipeline failed on {package.git.path_with_namespace}:{branch.name}, ignoring, {ignore_reason}"