Close http connection in perform method of Request class (#6889)

HTTP connections must be explicitly closed in many cases, and letting
perform method close connections makes its callers less redundant and
prevent them from forgetting to close connections.

app/helpers/jsonld_helper.rb

@@ -60,9 +60,9 @@ module JsonLdHelper
   end
 
   def fetch_resource_without_id_validation(uri)
-    response = build_request(uri).perform
-    return if response.code != 200
-    body_to_json(response.to_s)
+    build_request(uri).perform do |response|
+      response.code == 200 ? body_to_json(response.to_s) : nil
+    end
   end
 
   def body_to_json(body)