[Store] Fix Retriever example to use correct option name

InMemoryStore uses `maxItems` option to limit results, not `limit`.

Author: OskarStark

examples/retriever/basic.php

@@ -45,7 +45,7 @@
 );
 
 echo "Searching for: 'Roman gladiator revenge'\n\n";
-$results = $retriever->retrieve('Roman gladiator revenge', ['limit' => 1]);
+$results = $retriever->retrieve('Roman gladiator revenge', ['maxItems' => 1]);
 
 foreach ($results as $i => $document) {
     echo sprintf("%d. Document ID: %s\n", $i + 1, $document->id);

src/store/tests/RetrieverTest.php

@@ -93,7 +93,7 @@ public function testRetrievePassesOptionsToStore()
         );
 
         $retriever = new Retriever($vectorizer, $store);
-        $results = iterator_to_array($retriever->retrieve('test query', ['limit' => 10]));
+        $results = iterator_to_array($retriever->retrieve('test query', ['maxItems' => 10]));
 
         $this->assertCount(1, $results);
     }