Remove dependency on `gd2-ffij`

[pablobm]

We have a dependency on the gem gd2-ffij, which is currently unmaintained and for which we already have had to introduce a dubious workaround: #6408

What is the impact? Are there alternatives? Can we remove it altogether? Perhaps SVG-based?

[pablobm]

Potential way to address it? https://github.com/openstreetmap-ng/openstreetmap-ng/blob/main/app/views/traces/_svg.ts

[gravitystorm]

Please don't consider using code from that project - it has an incompatible licence (AGPLv3).

[Firefishy]

Please don't consider using code from that project - it has an incompatible licence (AGPLv3).

Sorry, that was my mistake, I pointed @pablobm at the project. I wasn't aware it used a different licence.

[mmd-osm]

I implemented an SVG based version (without using anything from that AGLPv3 project) some time ago: https://github.com/mmd-osm/openstreetmap-website/tree/feature/gpximage

It still has lots of rough edges and is more of a prototype for playing around with.