Remove crate: calx-ecs

[stefnotch]

Please remove crate from category: ECS

I think this ECS library is small enough and hasn't been updated since 2018 to warrant being removed from the list
https://github.com/rsaarelm/calx-ecs

[AngelOnFira]

There's more discussion about this kind of thing in #95, not sure what the current way to proceed is though.