Sets static port for vnc (fixes #47)

[domna]

Not using the static port breaks the image, rendering it unusable. This essentially reverts commit https://github.com/jupyterhub/jupyter-remote-desktop-proxy/commit/447bf86d66bced05e5a02160f2eb5c0739994b68 to fix this

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[github-actions[bot]]

:point_left: Launch a binder notebook on this branch for commit c782eb963ce8067be8f3278525157ca4fa5dce22

I will automatically update this comment whenever this PR is modified

[yuvipanda]

Opened https://github.com/jupyterhub/jupyter-remote-desktop-proxy/pull/53 instead