Remove dead overlay code from EngineState

crates/nu-protocol/src/engine/engine_state.rs

@@ -357,13 +357,6 @@ impl EngineState {
         Ok(())
     }
 
-    pub fn has_overlay(&self, name: &[u8]) -> bool {
-        self.scope
-            .overlays
-            .iter()
-            .any(|(overlay_name, _)| name == overlay_name)
-    }
-
     pub fn active_overlay_ids<'a, 'b>(
         &'b self,
         removed_overlays: &'a [Vec<u8>],