docs: fix outdated comment
# FIXME: We currently have some code duplicated in
# binderhub/binderspawner_mixin.py and helm-chart/binderhub/values.yaml
# and we use a pre-commit hook to automatically update the values in
-# values.yaml whenever binderhub/binderspawner_mixin.py is changed.
+# values.yaml.
#
# We should remove the embedded code from values.yaml and install the required
# BinderSpawner code in the JupyterHub container.
