Update article.md

Maybe this is what you want. "Complexity" is singular, so if that's the antecedent, one would use "was".

1-js/06-advanced-functions/09-call-apply-decorators/article.md

@@ -58,7 +58,7 @@ From an outside code, the wrapped `slow` function still does the same. It just g
 To summarize, there are several benefits of using a separate `cachingDecorator` instead of altering the code of `slow` itself:
 
 - The `cachingDecorator` is reusable. We can apply it to another function.
-- The caching logic is separate, it did not increase the complexity of `slow` itself (if there were any).
+- The caching logic is separate, it did not increase the complexity of `slow` itself (if there was any).
 - We can combine multiple decorators if needed (other decorators will follow).