Fix warnings ":logger is used by the current application but the current application does not depend on :logger"

During compilation, we had the following warning which is now fixed

```
==> restarter
Compiling 1 file (.ex)
warning: Logger.__do_log__/4 defined in application :logger is used by the current application but the current application does not depend on :logger. To fix this, you must do one of:

  1. If :logger is part of Erlang/Elixir, you must include it under :extra_applications inside "def application" in your mix.exs

  2. If :logger is a dependency, make sure it is listed under "def deps" in your mix.exs

  3. In case you don't want to add a requirement to :logger, you may optionally skip this warning by adding [xref: [exclude: [Logger]]] to your "def project" in mix.exs

Invalid call found at 2 locations:
  lib/pleroma.ex:65: Restarter.Pleroma.handle_cast/2
  lib/pleroma.ex:78: Restarter.Pleroma.handle_cast/2

warning: Logger.__should_log__/2 defined in application :logger is used by the current application but the current application does not depend on :logger. To fix this, you must do one of:

  1. If :logger is part of Erlang/Elixir, you must include it under :extra_applications inside "def application" in your mix.exs

  2. If :logger is a dependency, make sure it is listed under "def deps" in your mix.exs

  3. In case you don't want to add a requirement to :logger, you may optionally skip this warning by adding [xref: [exclude: [Logger]]] to your "def project" in mix.exs

Invalid call found at 2 locations:
  lib/pleroma.ex:65: Restarter.Pleroma.handle_cast/2
  lib/pleroma.ex:78: Restarter.Pleroma.handle_cast/2

warning: Logger.debug/1 defined in application :logger is used by the current application but the current application does not depend on :logger. To fix this, you must do one of:

  1. If :logger is part of Erlang/Elixir, you must include it under :extra_applications inside "def application" in your mix.exs

  2. If :logger is a dependency, make sure it is listed under "def deps" in your mix.exs

  3. In case you don't want to add a requirement to :logger, you may optionally skip this warning by adding [xref: [exclude: [Logger]]] to your "def project" in mix.exs

Invalid call found at 2 locations:
  lib/pleroma.ex:65: Restarter.Pleroma.handle_cast/2
  lib/pleroma.ex:78: Restarter.Pleroma.handle_cast/2
```

restarter/mix.exs

@@ -13,7 +13,8 @@ defmodule Restarter.MixProject do
 
   def application do
     [
-      mod: {Restarter, []}
+      mod: {Restarter, []},
+      extra_applications: [:logger]
     ]
   end