Remove unused (#2501)

* Remove Moxa

- [Undetected](https://www.wappalyzer.com/technologies/moxa)
- [Website](https://www.moxa.com/) says "Industrial IOT", unlikely to be
  detected/useful

* Remove Sparql

- [undetected](https://www.wappalyzer.com/technologies/sparql)
- no way to be detected, must have been a dependency at some point in the past

* Remove ARC Forum

- [Undetected](https://www.wappalyzer.com/technologies/arc-forum)
- The [website](AAA) says: "This site is about Arc, a new dialect of Lisp.",
  and also "Arc is unfinished. It's missing things you'd need to solve some types of problems. But it works well for basic web apps.".
  I dont think that anyone is using it in production

* Remove C++, since it can't be detected

* Remove Gazelle

- What.cd is dead
- The project isn't maintained anymore