Upgrade Comeonin to v5

https://github.com/riverrun/comeonin/blob/master/UPGRADE_v5.md

mix.exs

@@ -126,8 +126,7 @@ defmodule Pleroma.Mixfile do
       {:postgrex, ">= 0.13.5"},
       {:oban, "~> 1.2"},
       {:gettext, "~> 0.15"},
-      {:comeonin, "~> 4.1.1"},
-      {:pbkdf2_elixir, "~> 0.12.3"},
+      {:pbkdf2_elixir, "~> 1.0"},
       {:trailing_format_plug, "~> 0.0.7"},
       {:fast_sanitize, "~> 0.1"},
       {:html_entities, "~> 0.5", override: true},