Set ex_doc dependency to >= 0.40.0

Author: FelonEkonom

mix.exs

@@ -47,7 +47,7 @@ defmodule Membrane.H264.FFmpeg.Plugin.MixProject do
       {:membrane_common_c, "~> 0.16.0"},
       {:membrane_h264_format, "~> 0.6.1"},
       {:membrane_raw_video_format, "~> 0.4.1"},
-      {:ex_doc, "~> 0.40", only: :dev, runtime: false},
+      {:ex_doc, ">= 0.40.0", only: :dev, runtime: false},
       {:credo, ">= 0.0.0", only: :dev, runtime: false},
       {:dialyxir, ">= 0.0.0", only: :dev, runtime: false},
       {:membrane_raw_video_parser_plugin, "~> 0.12.2", only: :test},