Fix new credo warnings

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/federation/web_finger/xml_builder.ex

@@ -39,9 +39,7 @@ defmodule Mobilizon.Federation.WebFinger.XmlBuilder do
   defp to_xml(content) when is_binary(content), do: to_string(content)
 
   defp to_xml(content) when is_list(content) do
-    content
-    |> Enum.map(&to_xml/1)
-    |> Enum.join()
+    Enum.map_join(content, &to_xml/1)
   end
 
   defp to_xml(%NaiveDateTime{} = time), do: NaiveDateTime.to_iso8601(time)
@@ -49,9 +47,7 @@ defmodule Mobilizon.Federation.WebFinger.XmlBuilder do
   @spec make_open_tag(tag :: atom, attributes :: map()) :: String.t()
   defp make_open_tag(tag, attributes) do
     attributes_string =
-      attributes
-      |> Enum.map(fn {attribute, value} -> "#{attribute}=\"#{value}\"" end)
-      |> Enum.join(" ")
+      Enum.map_join(attributes, " ", fn {attribute, value} -> "#{attribute}=\"#{value}\"" end)
 
     [to_string(tag), attributes_string] |> Enum.join(" ") |> String.trim()
   end