Use new default_formatter

mix_tests/config/config.exs

@@ -11,21 +11,13 @@ config :logger,
   level: :info,
   utc_log: true
 
-# Configures Elixir's Logger
-config :logger, :console,
-  format: "$time $metadata[$level] $message\n",
-  metadata: [:request_id, :trace_id, :span_id]
-
-config :logger_formatter_json_tests, :logger, [
-  {:handler, :default, :logger_std_h,
-   %{
-     formatter:
-       {:logger_formatter_json,
-        %{
-          names: :datadog
-        }}
-   }}
-]
+config :logger, :default_handler,
+  formatter: {
+    :logger_formatter_json,
+    %{
+      names: :datadog
+    }
+  }
 
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.