fix: incompatible methods

Author: KondukterCRO

src/Model/Collection/ArrayCollection.php

@@ -39,7 +39,7 @@ public function count(): int
         return $this->count;
     }
 
-    public function getIterator()
+    public function getIterator(): \Traversable
     {
         return new ArrayIterator($this->getItems());
     }

src/Model/Collection/UniqueResourceCollection.php

@@ -56,7 +56,7 @@ public function getResources(): array
         return $this->items;
     }
 
-    public function getIterator()
+    public function getIterator(): \Traversable
     {
         return new ArrayIterator($this->items);
     }