kf-notebook Dockerfile: upgrade Jupyter base image from v1.4 to v1.5

[ptitzler]

Update the Kubeflow notebook server Dockerfile to use the latest Jupyter image.

What changes were proposed in this pull request?

Upgrade base image dependency from 1.4 to 1.5

How was this pull request tested?

• Built container image and deployed it on Kubeflow as a notebook server

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