chore(deps): update dependency cowboy to v2

mix.exs

@@ -37,7 +37,7 @@ defmodule Eblog.Mixfile do
      {:phoenix_html, "== 2.14.3"},
      {:phoenix_live_reload, "== 1.3.3", only: :dev},
      {:gettext, "== 0.19.1"},
-     {:cowboy, "== 1.1.2"}]
+     {:cowboy, "== 2.9.0"}]
   end
 
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