Fix alertNode redux schema bug by updating prop on rule correctly

ui/src/kapacitor/reducers/rules.js

@@ -172,8 +172,10 @@ export default function rules(state = {}, action) {
 
       return {
         ...state,
-        [ruleID]: {...state[ruleID]},
+        [ruleID]: {
+          ...state[ruleID],
           alertNodes: newAlertNodes,
+        },
       }
     }