Versions in Dependancies are incorrect

The URL

https://inkscape.gitlab.io/extensions/python-dependencies.txt

Reports the python deps with a specific version, but these are not versions required but just the version that was installed by the CI builder. Which is good in that it means the code was tested against this version, but bad in that this version is so new it's unlikely to be available for some platforms and we loose information about what the minimum version that our extensions work against.

TODO:

Add a way to record the minimum versions and if we should test against them.