avoid mix format bug

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -765,7 +765,7 @@ def fetch_and_contain_remote_object_from_id(id) do
          {:ok, %{body: body, status: code}} when code in 200..299 <-
            @httpoison.get(
              id,
-             Accept: "application/activity+json"
+             [{:Accept, "application/activity+json"}]
            ),
          {:ok, data} <- Jason.decode(body),
          :ok <- Transmogrifier.contain_origin_from_id(id, data) do

lib/pleroma/web/ostatus/ostatus.ex

@@ -349,7 +349,7 @@ def fetch_activity_from_atom_url(url) do
          {:ok, %{body: body, status: code}} when code in 200..299 <-
            @httpoison.get(
              url,
-             Accept: "application/atom+xml"
+             [{:Accept, "application/atom+xml"}]
            ) do
       Logger.debug("Got document from #{url}, handling...")
       handle_incoming(body)