Bump ex_doc from 0.20.1 to 0.20.2

Bumps [ex_doc](https://github.com/elixir-lang/ex_doc) from 0.20.1 to 0.20.2.
- [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@v0.20.1...v0.20.2)

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

mix.lock

@@ -3,7 +3,7 @@
   "certifi": {:hex, :certifi, "2.5.1", "867ce347f7c7d78563450a18a6a28a8090331e77fa02380b4a21962a65d36ee5", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm"},
   "credo": {:hex, :credo, "0.9.2", "841d316612f568beb22ba310d816353dddf31c2d94aa488ae5a27bb53760d0bf", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:poison, ">= 0.0.0", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
   "earmark": {:hex, :earmark, "1.3.2", "b840562ea3d67795ffbb5bd88940b1bed0ed9fa32834915125ea7d02e35888a5", [:mix], [], "hexpm"},
-  "ex_doc": {:hex, :ex_doc, "0.20.1", "88eaa16e67c505664fd6a66f42ddb962d424ad68df586b214b71443c69887123", [:mix], [{:earmark, "~> 1.3", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.10", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
+  "ex_doc": {:hex, :ex_doc, "0.20.2", "1bd0dfb0304bade58beb77f20f21ee3558cc3c753743ae0ddbb0fd7ba2912331", [:mix], [{:earmark, "~> 1.3", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.10", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
   "exactor": {:hex, :exactor, "2.2.4", "5efb4ddeb2c48d9a1d7c9b465a6fffdd82300eb9618ece5d34c3334d5d7245b1", [], [], "hexpm"},
   "excoveralls": {:hex, :excoveralls, "0.10.6", "e2b9718c9d8e3ef90bc22278c3f76c850a9f9116faf4ebe9678063310742edc2", [:mix], [{:hackney, "~> 1.13", [hex: :hackney, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm"},
   "exjsx": {:hex, :exjsx, "4.0.0", "60548841e0212df401e38e63c0078ec57b33e7ea49b032c796ccad8cde794b5c", [], [{:jsx, "~> 2.8.0", [hex: :jsx, repo: "hexpm", optional: false]}], "hexpm"},