Revert #1682 (three-axis milling) (#1715)

Thanks @bherbruck.

crates/engine/src/cmd/mod.rs

@@ -21,7 +21,6 @@ macro_rules! planned {
 }
 
 mod browser;
-mod cam;
 mod clipboard;
 mod compare;
 mod component;
@@ -253,7 +252,6 @@ pub fn command_specs() -> Vec<&'static CommandSpec> {
     v.extend(component_link::COMMANDS.iter());
     v.extend(joints::COMMANDS.iter());
     v.extend(motion::COMMANDS.iter());
-    v.extend(cam::COMMANDS.iter());
     v.extend(config::COMMANDS.iter());
     v.extend(parts::COMMANDS.iter());
     v.extend(browser::COMMANDS.iter());