fix lowest supported Serializer version

xabbuh · xabbuh · commit bb7058a5aad3 · 2018-02-23T14:04:00.000+01:00
The `AbstractObjectNormalizer::setMaxDepthHandler()` method does not
exist before `symfony/serializer` 4.1.
diff --git a/composer.json b/composer.json
@@ -67,7 +67,7 @@
         "symfony/console": "<3.4",
         "symfony/form": "<3.4",
         "symfony/property-info": "<3.4",
-        "symfony/serializer": "<3.4",
+        "symfony/serializer": "<4.1",
         "symfony/stopwatch": "<3.4",
         "symfony/translation": "<3.4",
         "symfony/validator": "<4.1",
