Remove Copy implementation from all objects

It seems unexpected an unnecessary, as evidenced by the fact that it
wasn't actually used anywhere. It also seems potentially error-prone,
although I can't come up with specific examples right now.

Either way, it's probably worth removing for the consistency alone.

crates/fj-core/src/objects/kinds/surface.rs

@@ -14,7 +14,7 @@
 /// If you need to reference a `Surface` from a struct that needs to derive
 /// `Eq`/`Ord`/..., you can use `HandleWrapper<Vertex>` to do that. It will
 /// use `Handle::id` to provide those `Eq`/`Ord`/... implementations.
-#[derive(Clone, Copy, Debug, Default)]
+#[derive(Clone, Debug, Default)]
 pub struct Surface {}
 
 impl Surface {

crates/fj-core/src/objects/kinds/vertex.rs

@@ -83,7 +83,7 @@
 /// [`Sketch`]: crate::objects::Sketch
 /// [`Solid`]: crate::objects::Solid
 /// [`Surface`]: crate::objects::Surface
-#[derive(Clone, Copy, Debug, Default)]
+#[derive(Clone, Debug, Default)]
 pub struct Vertex {}
 
 impl Vertex {