feat: don't use nightly features

crates/nocontrol/src/lib.rs

@@ -1,5 +1,3 @@
-#![feature(associated_type_defaults)]
-
 mod control_plane;
 pub use control_plane::ControlPlane;
 

crates/nocontrol/src/operator.rs

@@ -9,7 +9,7 @@ pub trait Specification: Clone + Serialize + DeserializeOwned {
 #[allow(dead_code, unused_variables)]
 pub trait Operator: Send + Sync + 'static {
     type Specifications: Specification;
-    type Error = anyhow::Error;
+    type Error;
 
     fn reconcile(
         &self,

crates/nocontrol/tests/mod.rs

@@ -51,6 +51,7 @@ pub struct MyOperator {}
 
 impl Operator for MyOperator {
     type Specifications = Specifications;
+    type Error = anyhow::Error;
 
     async fn reconcile(
         &self,