fix delete call for article

Author: spicquenot

dataikuapi/dss/wiki.py

@@ -100,7 +100,7 @@ def delete(self):
         """
         Delete the article
         """
-        return self.client._perform_json("DELETE", "/projects/%s/wiki/%s" % (self.project_key, self.article_id))
+        self.client._perform_empty("DELETE", "/projects/%s/wiki/%s" % (self.project_key, self.article_id))
 
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