fix: js how can you change the casing of a string code example (freeCodeCamp#57556)

Author: scissorsneedfoodtoo

curriculum/challenges/english/25-front-end-development/lecture-working-with-common-string-methods/67326c1fdaf9c0c5ad1a2589.md

@@ -53,7 +53,7 @@ Think about how `toUpperCase()` affects the entire string.
 What will the following code output?
 
 ```js
-javascriptCopy codelet phrase = "JavaScript is Fun!";
+let phrase = "JavaScript is Fun!";
 console.log(phrase.toLowerCase());
 ```