Update createSlice.mdx

```
store.dispatch(counter.actions.increment())
// -> { counter: 1, user: {name : '', age: 21} }
store.dispatch(counter.actions.increment())
// -> { counter: 2, user: {name: '', age: 22} }
store.dispatch(counter.actions.multiply(3))
// -> { counter: 6, user: {name: '', age: 22} }
store.dispatch(counter.actions.multiply())
// -> { counter: 12, user: {name: '', age: 22} }
console.log(`${counter.actions.decrement}`)
// -> "counter/decrement"
store.dispatch(user.actions.setUserName('eric'))
// -> { counter: 12, user: { name: 'eric', age: 22} }
```

last lint should be counter : 12 not counter : 6

Author: AbdelhamidGamal

docs/api/createSlice.mdx

@@ -287,5 +287,5 @@ store.dispatch(counter.actions.multiply())
 console.log(`${counter.actions.decrement}`)
 // -> "counter/decrement"
 store.dispatch(user.actions.setUserName('eric'))
-// -> { counter: 6, user: { name: 'eric', age: 22} }
+// -> { counter: 12, user: { name: 'eric', age: 22} }
 ```