JS: Add overlay[local] to restore magic in unwrap() predicate

In this case we actually want magic to apply, but was prevented by locality.

javascript/ql/lib/LanguageFeatures/UnusedIndexVariable.qll

@@ -1,6 +1,8 @@
 /**
  * Provides a predicate for identifying unused index variables in loops.
  */
+overlay[local]
+module;
 
 import javascript