Fix similar docs code sample

Author: norkunas

.code-samples.meilisearch.yaml

@@ -743,7 +743,7 @@ search_parameter_guide_matching_strategy_3: |-
   $client->index('movies')->search('white shirt', ['matchingStrategy' => 'frequency']);
 get_similar_post_1: |-
   $similarQuery = new SimilarDocumentsQuery('TARGET_DOCUMENT_ID');
-  $client->index('INDEX_NAME')->getSimilar($similarQuery);
+  $client->index('INDEX_NAME')->searchSimilarDocuments($similarQuery);
 multi_search_federated_1: |-
   $client->multiSearch([
       (new SearchQuery())