Drop derelict_canal rendering

[sommerluk]

Resolves #1003

[kocio-pl]

Do you think it's better to just drop it now than count on wiki changes that could clarify it? There were some changes recently:

https://wiki.openstreetmap.org/wiki/Tag:waterway%3Dderelict_canal

[sommerluk]

I think indeed that dropping now it is the best solution.

[kocio-pl]

I think that you're right - it can look in many ways: filled with water, intermittent water, ditch, ditch filled with plants etc., so there's no reasonable way of rendering it. Even proposed tags with prefixes still are unclear in this regard, so we need some more precise tagging to visualize it.

[kocio-pl]

Thanks, testing looks OK.