style(server): remove unused get_full_graph method to clear clippy warning

server/src/state.rs

@@ -64,10 +64,6 @@ impl MemoryState {
         let _ = self.activity_tx.send(payload);
     }
 
-    pub fn get_full_graph(&self) -> KnowledgeGraph {
-        self.graph.read_with(|g| g.clone())
-    }
-
     pub fn read_graph<F, R>(&self, f: F) -> R
     where
         F: FnOnce(&KnowledgeGraph) -> R,