build(deps-dev): bump mix_test_watch from 0.8.0 to 0.9.0

Bumps [mix_test_watch](https://github.com/lpil/mix-test.watch) from 0.8.0 to 0.9.0.
- [Release notes](https://github.com/lpil/mix-test.watch/releases)
- [Changelog](https://github.com/lpil/mix-test.watch/blob/master/CHANGELOG.md)
- [Commits](lpil/mix-test.watch@v0.8.0...v0.9.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Author: dependabot-support

mix.lock

@@ -36,7 +36,7 @@
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm"},
   "mime": {:hex, :mime, "1.3.0", "5e8d45a39e95c650900d03f897fbf99ae04f60ab1daa4a34c7a20a5151b7a5fe", [:mix], [], "hexpm"},
   "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [:rebar3], [], "hexpm"},
-  "mix_test_watch": {:hex, :mix_test_watch, "0.8.0", "acf97da2abc66532e7dc1aa66a5d6c9fc4442d7992d5d7eb4faeaeb964c2580e", [:mix], [{:file_system, "~> 0.2.1 or ~> 0.3", [hex: :file_system, repo: "hexpm", optional: false]}], "hexpm"},
+  "mix_test_watch": {:hex, :mix_test_watch, "0.9.0", "c72132a6071261893518fa08e121e911c9358713f62794a90c95db59042af375", [:mix], [{:file_system, "~> 0.2.1 or ~> 0.3", [hex: :file_system, repo: "hexpm", optional: false]}], "hexpm"},
   "parse_trans": {:hex, :parse_trans, "3.2.0", "2adfa4daf80c14dc36f522cf190eb5c4ee3e28008fc6394397c16f62a26258c2", [:rebar3], [], "hexpm"},
   "phoenix": {:hex, :phoenix, "1.3.4", "aaa1b55e5523083a877bcbe9886d9ee180bf2c8754905323493c2ac325903dc5", [:mix], [{:cowboy, "~> 1.0", [hex: :cowboy, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 1.0", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:plug, "~> 1.3.3 or ~> 1.4", [hex: :plug, repo: "hexpm", optional: false]}, {:poison, "~> 2.2 or ~> 3.0", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix_ecto": {:hex, :phoenix_ecto, "3.4.0", "91cd39427006fe4b5588d69f0941b9c3d3d8f5e6477c563a08379de7de2b0c58", [:mix], [{:ecto, "~> 2.1", [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"},