MastodonApi: Bump api level.

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

@@ -159,7 +159,7 @@ def user(%{assigns: %{user: for_user}} = conn, %{"id" => nickname_or_id}) do
     end
   end
 
-  @mastodon_api_level "2.5.0"
+  @mastodon_api_level "2.6.5"
 
   def masto_instance(conn, _params) do
     instance = Config.get(:instance)