Update dependency gettext to ~> 0.23 (#106)

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This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [gettext](https://hex.pm/packages/gettext) | minor | `~> 0.11` -> `~>
0.23` |

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mix.exs

@@ -36,7 +36,7 @@ defmodule Nisse.MixProject do
       {:credo, "~> 1.5", only: [:dev, :test], runtime: false},
       {:ecto_sql, "~> 3.4"},
       {:floki, ">= 0.0.0", only: :test},
-      {:gettext, "~> 0.11"},
+      {:gettext, "~> 0.23"},
       {:jason, "~> 1.0"},
       {:phoenix, "~> 1.6.0"},
       {:phoenix_ecto, "~> 4.1"},