component/jupyter-py2: move traitlets python2 pin in stack/slapos

Following up on 6506625f (software/jupyter: Move pinned eggs to
slapos.cfg, 2023-01-06), we need to keep a traitlets pin that is
compatible with python2, for component/pygolang/test-py2.cfg

component/jupyter-py2/buildout.cfg

@@ -75,7 +75,6 @@ scikit-learn = 0.18.1
 statsmodels = 0.8.0
 terminado = 0.6
 tornado = 4.4.2
-traitlets = 4.3.3
 
 # nbconvert 4.2.0 depends on entrypoints egg that is not available as tar/zip source.
 nbconvert = 4.1.0

stack/slapos.cfg

@@ -338,6 +338,7 @@ feedparser = 5.2.1
 pyparsing = 2.2.0
 pyrsistent = 0.16.1
 requests = 2.27.1
+traitlets = 4.3.3
 Werkzeug = 1.0.1
 
 [versions:sys.version_info < (3,8)]