Issue #3320157 by citlacom: PHP8 deprecated function return type of...

Issue #3320157 by citlacom: PHP8 deprecated function return type of JSComponentAttachment getIterator

src/JSComponentAttachment.php

@@ -56,7 +56,7 @@ class JSComponentAttachment implements \IteratorAggregate {
   /**
    * {@inheritDoc}
    */
-  public function getIterator() {
+  public function getIterator(): \ArrayIterator {
     return new \ArrayIterator($this->attached);
   }
 }