fix: js extract a substring multiple choice code example (freeCodeCamp#57555)

Author: scissorsneedfoodtoo

curriculum/challenges/english/25-front-end-development/lecture-working-with-common-string-methods/67326c15b3b2f0c5827927cc.md

@@ -18,7 +18,7 @@ What will the following code output?
 
 ```js
 let text = "JavaScript is awesome!";
-let result = text.slice(0, 10);
+let result = text.slice(0, 9);
 
 console.log(result);
 ```
@@ -97,7 +97,7 @@ What will the following code return?
 
 ```js
 let sentence = "Learning JavaScript is fun!";
-let extracted = sentence.slice(9, -4);
+let extracted = sentence.slice(9, -5);
 
 console.log(extracted);
 ```