Fix usage of is_bitstring instead of is_binary

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

lib/federation/activity_pub/refresher.ex

@@ -127,7 +127,7 @@ defmodule Mobilizon.Federation.ActivityPub.Refresher do
        do: process_collection(first, on_behalf_of)
 
   defp process_collection(%{"type" => "OrderedCollection", "first" => first}, on_behalf_of)
-       when is_bitstring(first) do
+       when is_binary(first) do
     Logger.debug("OrderedCollection has a first property pointing to an URI")
 
     with {:ok, data} <- Fetcher.fetch(first, on_behalf_of: on_behalf_of) do

lib/federation/activity_pub/relay.ex

@@ -126,7 +126,7 @@ defmodule Mobilizon.Federation.ActivityPub.Relay do
     end
   end
 
-  defp fetch_object(object) when is_bitstring(object), do: {object, object}
+  defp fetch_object(object) when is_binary(object), do: {object, object}
 
   @spec fetch_actor(String.t()) :: {:ok, String.t()} | {:error, String.t()}
   # Dirty hack

lib/federation/activity_pub/utils.ex

@@ -26,7 +26,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
   # Some implementations send the actor URI as the actor field, others send the entire actor object,
   # so figure out what the actor's URI is based on what we have.
   def get_url(%{"id" => id}), do: id
-  def get_url(id) when is_bitstring(id), do: id
+  def get_url(id) when is_binary(id), do: id
   def get_url(ids) when is_list(ids), do: get_url(hd(ids))
   def get_url(_), do: nil
 
@@ -223,7 +223,7 @@ defmodule Mobilizon.Federation.ActivityPub.Utils do
     end
   end
 
-  def get_actor(%{"actor" => %{"id" => id}}) when is_bitstring(id) do
+  def get_actor(%{"actor" => %{"id" => id}}) when is_binary(id) do
     id
   end