Iterate only own keys when clearing memoize cache

Replace a for..in loop over `this` with `Object.keys(this).forEach` to ensure only the object's own enumerable properties are inspected when clearing memoize caches. This avoids iterating inherited/prototype properties that could lead to unexpected behavior when resetting cached entries in workers/grouper/src/index.ts.

Author: talyguryn

workers/grouper/src/index.ts

@@ -159,15 +159,15 @@ export default class GrouperWorker extends Worker {
      */
     const memoizeCachePrefix = 'memoizeCache:';
 
-    for (const key in this) {
+    Object.keys(this).forEach(key => {
       if (key.startsWith(memoizeCachePrefix)) {
         const cache = this[key] as any;
 
         if (cache && typeof cache.reset === 'function') {
           cache.reset();
         }
       }
-    }
+    });
   }
 
   /**