chore(ci): bump checkout to v6

[okurz]

This also fixes a warning about outdated nodejs

[kalikiana]

Run black -l 120 --check --diff openqa_bugfetcher/
--- /home/runner/work/openqa_bugfetcher/openqa_bugfetcher/openqa_bugfetcher/issues/bugzilla_issue.py	2026-04-12 16:40:33.096165+00:00
+++ /home/runner/work/openqa_bugfetcher/openqa_bugfetcher/openqa_bugfetcher/issues/bugzilla_issue.py	2026-04-12 16:40:39.057010+00:00
@@ -1,11 +1,10 @@
 import html
 
 import requests
 
 from openqa_bugfetcher.issues import BaseIssue
-

Somehow this results in a difference of a line break? 🤔

[okurz]

Somehow this results in a difference of a line break? 🤔

Well, it's not my changes causing this but a PR created in this slow moving projected triggering checks using more recent versions of checkers. This reveals now style issues which are already there. Note that also all Python versions in use here are older.