fix(curriculum): error in asserting initial state of redux store (#45457)

Initialize different store variable (_store) to prevent test failures in case user tested his own store in the exercise.

curriculum/challenges/english/03-front-end-development-libraries/redux/write-a-counter-with-redux.md

@@ -31,7 +31,7 @@ assert(decAction().type === DECREMENT);
 The Redux store should initialize with a `state` of 0.
 
 ```js
-assert(store.getState() === 0);
+assert(_store.getState() === 0);
 ```
 
 Dispatching `incAction` on the Redux store should increment the `state` by 1.
@@ -39,9 +39,9 @@ Dispatching `incAction` on the Redux store should increment the `state` by 1.
 ```js
 assert(
   (function () {
-    const initialState = store.getState();
-    store.dispatch(incAction());
-    const incState = store.getState();
+    const initialState = _store.getState();
+    _store.dispatch(incAction());
+    const incState = _store.getState();
     return initialState + 1 === incState;
   })()
 );
@@ -52,9 +52,9 @@ Dispatching `decAction` on the Redux store should decrement the `state` by 1.
 ```js
 assert(
   (function () {
-    const initialState = store.getState();
-    store.dispatch(decAction());
-    const decState = store.getState();
+    const initialState = _store.getState();
+    _store.dispatch(decAction());
+    const decState = _store.getState();
     return initialState - 1 === decState;
   })()
 );
@@ -83,6 +83,12 @@ const decAction = null; // Define an action creator for decrementing
 const store = null; // Define the Redux store here, passing in your reducers
 ```
 
+## --after-user-code--
+
+```js
+const _store = Redux.createStore(counterReducer)
+```
+
 # --solutions--
 
 ```js