Bump ex_doc from 0.21.1 to 0.21.2 (#109)

Bumps [ex_doc](https://github.com/elixir-lang/ex_doc) from 0.21.1 to 0.21.2.
- [Release notes](https://github.com/elixir-lang/ex_doc/releases)
- [Changelog](https://github.com/elixir-lang/ex_doc/blob/master/CHANGELOG.md)
- [Commits](elixir-lang/ex_doc@v0.21.1...v0.21.2)

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

mix.lock

@@ -7,7 +7,7 @@
   "dialyxir": {:hex, :dialyxir, "1.0.0-rc.6", "78e97d9c0ff1b5521dd68041193891aebebce52fc3b93463c0a6806874557d7d", [:mix], [{:erlex, "~> 0.2.1", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm"},
   "earmark": {:hex, :earmark, "1.4.0", "397e750b879df18198afc66505ca87ecf6a96645545585899f6185178433cc09", [:mix], [], "hexpm"},
   "erlex": {:hex, :erlex, "0.2.1", "cee02918660807cbba9a7229cae9b42d1c6143b768c781fa6cee1eaf03ad860b", [:mix], [], "hexpm"},
-  "ex_doc": {:hex, :ex_doc, "0.21.1", "5ac36660846967cd869255f4426467a11672fec3d8db602c429425ce5b613b90", [:mix], [{:earmark, "~> 1.3", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
+  "ex_doc": {:hex, :ex_doc, "0.21.2", "caca5bc28ed7b3bdc0b662f8afe2bee1eedb5c3cf7b322feeeb7c6ebbde089d6", [:mix], [{:earmark, "~> 1.3.3 or ~> 1.4", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
   "excoveralls": {:hex, :excoveralls, "0.11.0", "1427780f327902f099ef948bbc107b06a200a14a80e5badc1f9624d0f059235f", [:mix], [{:hackney, "~> 1.0", [hex: :hackney, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm"},
   "goldrush": {:hex, :goldrush, "0.1.9", "f06e5d5f1277da5c413e84d5a2924174182fb108dabb39d5ec548b27424cd106", [:rebar3], [], "hexpm"},
   "hackney": {:hex, :hackney, "1.15.1", "9f8f471c844b8ce395f7b6d8398139e26ddca9ebc171a8b91342ee15a19963f4", [:rebar3], [{:certifi, "2.5.1", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.4", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},