fix(openapi): correct example usage for 3.0

In OpenApi 3.0 in component schema properties only `example` is allowed.
Hence we convert examples to example.

Author: Fylax

src/OpenApi/Serializer/LegacyOpenApiNormalizer.php

@@ -45,6 +45,11 @@ public function normalize(mixed $object, ?string $format = null, array $context
                     }
                     unset($schemas[$name]['properties'][$property]['type']);
                 }
+
+                if (\is_array($value['examples'] ?? false)) {
+                    $schemas[$name]['properties'][$property]['example'] = $value['examples'];
+                    unset($schemas[$name]['properties'][$property]['examples']);
+                }
             }
         }