docs(entity): updated FAQ url for Redux docs (#2297)

https://redux.js.org/faq/organizing-state#can-i-put-functions-promises-or-other-non-serializable-items-in-my-store-state

projects/ngrx.io/content/guide/entity/index.md

@@ -20,4 +20,4 @@ Entity promotes the use of plain JavaScript objects when managing collections. *
 2. State will always be serializable allowing you to store and rehydrate from browser storage mechanisms like local storage.
 3. State can be inspected via the Redux Devtools.
 
-This is one of the [core principles](docs) of NgRx. The [Redux docs](https://redux.js.org/faq/organizingstate#can-i-put-functions-promises-or-other-non-serializable-items-in-my-store-state) also offers some more insight into this constraint.
+This is one of the [core principles](docs) of NgRx. The [Redux docs](https://redux.js.org/faq/organizing-state#can-i-put-functions-promises-or-other-non-serializable-items-in-my-store-state) also offers some more insight into this constraint.