Remove marker-offset property

[mfluehr]

This property doesn't seem to be a part of any spec anymore. cf. https://developer.mozilla.org/en-US/docs/Web/CSS/marker-offset

[teoli2003]

I'm not convinced we should remove it. I think we should probably move it to a new group "Abandoned proposals" or similar, so we can have the info in the page, and not have it integrated with the navigation of actual properties. That way people stumbling on them via a search engine found them (and are warned against them), while people looking for mask information won't see it.

[Elchi3]

I think MDN is about practical information and so is this data repo. Features of specifications that never got implemented and removed from later specs are just ideas, proposals, theoretical things, which aren't practically useful to our main audience: web developers. I doubt it is useful to other audiences like web standards people either. What's the reason to keep these? People shouldn't be searching for this in the first place as they were never able to use it. I'm not sure I buy the search argument in this case. I would be a slightly different story if this feature would have been implemented somewhere for a while, but this seems to have never left the mere idea space.

My proposal would be to remove this from the data and to delete the MDN page.

[teoli2003]

Sounds logical. MDN page deleted.