Update repeat-str.js

Author: joanne342

Sprint-3/2-practice-tdd/repeat-str.js

@@ -2,7 +2,7 @@ function repeatStr(str, count) {
   // Your implementation of this function must *not* call String.prototype.repeat (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat).
   // The goal is to re-implement that function, not to use it.
 if (count < 0) {
-    throw new Error("Something went wrong");
+    throw new Error("Negative count is not allowed");
 
   } else if (count === 0) {
     return "";