fix: Bump to base-notebook with JH 1.1.0 etc

[bitnik]

#1549 bumps jupyter/base-notebook:d4e60350af15 which has jhub 1.0.0 installed (https://hub.docker.com/r/jupyter/base-notebook/tags/?page=2), but because in Dockerfile pip install --upgrade jupyterhub is executed, at the end image has jhub 1.1.0.

Since jupyter/docker-stacks#992 is fixed, we can use the latest jupyter/base-notebook and dont have to manually upgrade jhub anymore.

[consideRatio]

We don't have to manually do it now, but will need to do that whenever there is a minor release or anything on JupyterHub before it has been merged in docker-stacks. I think I prefer to retain the update step to ensure we are always up to date with JupyterHub like we are quick to be in the hub image.

+1 on bumping the base-notebook tag, but could we retain the manual upgrade step of jupyterhub? I find it convenient with a very little drawback of potentially increasing the image size, I'm not sure.

[bitnik]

Hmm I understand your point. Then maybe we should upgrade it to JUPYTERHUB_VERSION
as we do in hub's dockerfile. What do you think?

We already have JUPYTERHUB_VERSION defined in chartpress.yaml:

zero-to-jupyterhub-k8s/chartpress.yaml

Lines 20 to 23 in 25a303b

	singleuser-sample:
	valuesPath: singleuser.image
	buildArgs:
	JUPYTERHUB_VERSION: 1.1.0

[consideRatio]

Yepp that sounds good to me @bitnik!