fix: fixed docs whitespaces

Author: AndreaPontrandolfo

docs/rules/ensure-matching-remove-event-listener.md

@@ -10,40 +10,32 @@ This rule aims at reminding developers to add the corrisponding removeEventListe
 
 Examples of **incorrect** code for this rule:
 
-```js
-
+```jsx
 // Missing a matching removeEventListener.
-
 useEffect(() => {
     window.addEventListener("keydown", handleUserKeyPress);
     return () => {
         doThis();
     };
 }, [])
-
 ```
 
-```js
-
+```jsx
 // Missing a cleanup function for the addEventListener.
-
 useEffect(() => {
     window.addEventListener("keydown", handleUserKeyPress);
 }, [])
-
 ```
 
 Examples of **correct** code for this rule:
 
-```js
-
+```jsx
 useEffect(() => {
     window.addEventListener("keydown", handleUserKeyPress);
     return () => {
     window.removeEventListener("keydown", handleUserKeyPress);
     };
 }, []);
-
 ```
 
 ## When Not To Use It