chore: Bump emqtt_failover from 0.3.2 to 0.4.0 (#921)

Bumps [emqtt_failover](https://gitlab.com/paulswartz/emqtt_failover) from 0.3.2 to 0.4.0.
- [Release notes](https://gitlab.com/paulswartz/emqtt_failover/tags)
- [Changelog](https://gitlab.com/paulswartz/emqtt_failover/blob/main/CHANGELOG.md)
- [Commits](https://gitlab.com/paulswartz/emqtt_failover/compare/v0.3.2...v0.4.0)

---
updated-dependencies:
- dependency-name: emqtt_failover
  dependency-version: 0.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

mix.lock

@@ -20,7 +20,7 @@
   "ehmon": {:git, "https://github.com/mbta/ehmon.git", "a83590e82c09e9e4d2fdf89f1b9473e1181acbcc", [branch: "master"]},
   "elixir_make": {:hex, :elixir_make, "0.8.3", "d38d7ee1578d722d89b4d452a3e36bcfdc644c618f0d063b874661876e708683", [:mix], [{:castore, "~> 0.1 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:certifi, "~> 2.0", [hex: :certifi, repo: "hexpm", optional: true]}], "hexpm", "5c99a18571a756d4af7a4d89ca75c28ac899e6103af6f223982f09ce44942cc9"},
   "email_checker": {:hex, :email_checker, "0.2.4", "2bf246646678c8a366f2f6d2394845facb87c025ceddbd699019d387726548aa", [:mix], [{:socket, "~> 0.3.1", [hex: :socket, repo: "hexpm", optional: true]}], "hexpm", "e4ac0e5eb035dce9c8df08ebffdb525a5d82e61dde37390ac2469222f723e50a"},
-  "emqtt_failover": {:hex, :emqtt_failover, "0.3.2", "d6ece68d3f691ad0c42787dbfb7ae7f48ed0400504b4697fcd63a56ba73ed9ee", [:mix], [{:backoff, "~> 1.1.6", [hex: :backoff, repo: "hexpm", optional: false]}], "hexpm", "69b1c0d53a4f9752c365dc9c13b8eaeb5ac9286540f326ca71cdf36ada8307c5"},
+  "emqtt_failover": {:hex, :emqtt_failover, "0.4.0", "6e81318116df4e4bdc2de8906531af5efc6f59aa71dc95b5cee16b4b9e980c4d", [:mix], [{:backoff, "~> 1.1.6", [hex: :backoff, repo: "hexpm", optional: false]}], "hexpm", "7ab1f734208489bac0d886ce63559a47c997f59b1b17b533fa4ca3777fff5115"},
   "erlex": {:hex, :erlex, "0.2.7", "810e8725f96ab74d17aac676e748627a07bc87eb950d2b83acd29dc047a30595", [:mix], [], "hexpm", "3ed95f79d1a844c3f6bf0cea61e0d5612a42ce56da9c03f01df538685365efb0"},
   "ex_aws": {:hex, :ex_aws, "2.6.0", "346e87e35e5df0b3c016a96fb30adf6001de102981a71648dfc3ce3ad04765af", [:mix], [{:configparser_ex, "~> 5.0", [hex: :configparser_ex, repo: "hexpm", optional: true]}, {:hackney, "~> 1.16", [hex: :hackney, repo: "hexpm", optional: true]}, {:jason, "~> 1.1", [hex: :jason, repo: "hexpm", optional: true]}, {:jsx, "~> 2.8 or ~> 3.0", [hex: :jsx, repo: "hexpm", optional: true]}, {:mime, "~> 1.2 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:req, "~> 0.5.10 or ~> 0.6 or ~> 1.0", [hex: :req, repo: "hexpm", optional: true]}, {:sweet_xml, "~> 0.7", [hex: :sweet_xml, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4.3 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "30729ee9cbaacda674a4e4260d74206fa89bcd712267c4eaf42a0fc34592c0b3"},
   "ex_aws_dynamo": {:hex, :ex_aws_dynamo, "4.2.2", "7f7975b14f9999749b1dfb5bfff87fd80367dffcc2fe2dfea5a540ac216f5fe3", [:mix], [{:ex_aws, ">= 2.4.0", [hex: :ex_aws, repo: "hexpm", optional: false]}], "hexpm", "e61ee3e6b9e25794592059cd81356ebfc57676d9ff82755316925bf7feca672e"},