chore(deps): update dependency postgrex to == 0.21.1

Author: renovate[bot]

mix.exs

@@ -33,7 +33,7 @@ defmodule Eblog.Mixfile do
     [{:phoenix, "== 1.6.16"},
      {:phoenix_pubsub, "== 1.1.2"},
      {:phoenix_ecto, "== 3.6.0"},
-     {:postgrex, "== 0.16.5"},
+     {:postgrex, "== 0.21.1"},
      {:phoenix_html, "== 2.14.3"},
      {:phoenix_live_reload, "== 1.3.3", only: :dev},
      {:gettext, "== 0.19.1"},