Adapt to the removal of `websockify` in `jupyter-remote-desktop-proxy`

[sunu]

websockify has been removed from jupyter-remote-desktop-proxy. We need to adapt accordingly. See jupyterhub/jupyter-remote-desktop-proxy#148 (comment) for more context.

[sunu]

Addressed in #4.

Once that's merged, we should update the pinned version in https://github.com/2i2c-org/nasa-qgis-image/blob/607df3f5c661332aeccfc3c9f85b20a7b44540a1/Dockerfile#L39 and also pin jupyter-remote-desktop-proxy in https://github.com/2i2c-org/nasa-qgis-image/blob/607df3f5c661332aeccfc3c9f85b20a7b44540a1/Dockerfile#L38 to > 3.0.0.