Update hooks-reference.md (#2364)

typo: "effects run [..], but you can [..] fire it" => "effects run [..], but you can [..] fire them"

content/docs/hooks-reference.md

@@ -111,7 +111,7 @@ Mutations, subscriptions, timers, logging, and other side effects are not allowe
 
 Instead, use `useEffect`. The function passed to `useEffect` will run after the render is committed to the screen. Think of effects as an escape hatch from React's purely functional world into the imperative world.
 
-By default, effects run after every completed render, but you can choose to fire it [only when certain values have changed](#conditionally-firing-an-effect).
+By default, effects run after every completed render, but you can choose to fire them [only when certain values have changed](#conditionally-firing-an-effect).
 
 #### Cleaning up an effect {#cleaning-up-an-effect}