use older version of phoenix framework

In the PR (#2566) phoenix
was updated to `1.4.9`. But apparently new changes cause web socket
connection to disconnect and connect again which shows `Connection
Closed` message. We should investigate this issue and update phoenix
framework after that - #2595

apps/block_scout_web/mix.exs

@@ -99,7 +99,7 @@ defmodule BlockScoutWeb.Mixfile do
       {:logger_file_backend, "~> 0.0.10"},
       {:math, "~> 0.3.0"},
       {:mock, "~> 0.3.0", only: [:test], runtime: false},
-      {:phoenix, "~> 1.4"},
+      {:phoenix, "== 1.4.0"},
       {:phoenix_ecto, "~> 4.0"},
       {:phoenix_html, "~> 2.10"},
       {:phoenix_live_reload, "~> 1.2", only: [:dev]},

mix.lock

@@ -81,7 +81,7 @@
   "optimal": {:hex, :optimal, "0.3.6", "46bbf52fbbbd238cda81e02560caa84f93a53c75620f1fe19e81e4ae7b07d1dd", [:mix], [], "hexpm"},
   "parallel_stream": {:hex, :parallel_stream, "1.0.6", "b967be2b23f0f6787fab7ed681b4c45a215a81481fb62b01a5b750fa8f30f76c", [:mix], [], "hexpm"},
   "parse_trans": {:hex, :parse_trans, "3.2.0", "2adfa4daf80c14dc36f522cf190eb5c4ee3e28008fc6394397c16f62a26258c2", [:rebar3], [], "hexpm"},
-  "phoenix": {:hex, :phoenix, "1.4.9", "746d098e10741c334d88143d3c94cab1756435f94387a63441792e66ec0ee974", [:mix], [{:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 1.1", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:plug, "~> 1.8.1 or ~> 1.9", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 1.0 or ~> 2.0", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm"},
+  "phoenix": {:hex, :phoenix, "1.4.0", "56fe9a809e0e735f3e3b9b31c1b749d4b436e466d8da627b8d82f90eaae714d2", [:mix], [{:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 1.1", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 1.0 or ~> 2.0", [hex: :plug_cowboy, repo: "hexpm", optional: true]}], "hexpm"},
   "phoenix_ecto": {:hex, :phoenix_ecto, "4.0.0", "c43117a136e7399ea04ecaac73f8f23ee0ffe3e07acfcb8062fe5f4c9f0f6531", [:mix], [{:ecto, "~> 3.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:phoenix_html, "~> 2.9", [hex: :phoenix_html, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix_form_awesomplete": {:hex, :phoenix_form_awesomplete, "0.1.5", "d09aade160b584e3428e1e095645482396f17bddda4f566f1118f12d2598d11c", [:mix], [{:phoenix_html, "~> 2.10", [hex: :phoenix_html, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix_html": {:hex, :phoenix_html, "2.13.3", "850e292ff6e204257f5f9c4c54a8cb1f6fbc16ed53d360c2b780a3d0ba333867", [:mix], [{:plug, "~> 1.5", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},