Bump oauth2 from 0.9.4 to 2.0.0

Bumps [oauth2](https://github.com/scrogson/oauth2) from 0.9.4 to 2.0.0.
- [Release notes](https://github.com/scrogson/oauth2/releases)
- [Changelog](https://github.com/scrogson/oauth2/blob/master/CHANGELOG.md)
- [Commits](ueberauth/oauth2@v0.9.4...v2.0.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

mix.exs

@@ -43,7 +43,7 @@ defmodule UeberauthVK.Mixfile do
    [
      # Auth:
      {:ueberauth, "~> 0.4"},
-     {:oauth2, "~> 0.9"},
+     {:oauth2, "~> 2.0"},
 
      # Tests:
      {:exvcr, "~> 0.10", only: :test},

mix.lock

@@ -19,7 +19,7 @@
   "mime": {:hex, :mime, "1.3.1", "30ce04ab3175b6ad0bdce0035cba77bba68b813d523d1aac73d9781b4d193cf8", [:mix], [], "hexpm"},
   "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm"},
   "nimble_parsec": {:hex, :nimble_parsec, "0.5.0", "90e2eca3d0266e5c53f8fbe0079694740b9c91b6747f2b7e3c5d21966bba8300", [:mix], [], "hexpm"},
-  "oauth2": {:hex, :oauth2, "0.9.4", "632e8e8826a45e33ac2ea5ac66dcc019ba6bb5a0d2ba77e342d33e3b7b252c6e", [:mix], [{:hackney, "~> 1.7", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
+  "oauth2": {:hex, :oauth2, "2.0.0", "338382079fe16c514420fa218b0903f8ad2d4bfc0ad0c9f988867dfa246731b0", [:mix], [{:hackney, "~> 1.13", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
   "parse_trans": {:hex, :parse_trans, "3.3.0", "09765507a3c7590a784615cfd421d101aec25098d50b89d7aa1d66646bc571c1", [:rebar3], [], "hexpm"},
   "plug": {:hex, :plug, "1.7.2", "d7b7db7fbd755e8283b6c0a50be71ec0a3d67d9213d74422d9372effc8e87fd1", [:mix], [{:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.0", [hex: :plug_crypto, repo: "hexpm", optional: false]}], "hexpm"},
   "plug_crypto": {:hex, :plug_crypto, "1.0.0", "18e49317d3fa343f24620ed22795ec29d4a5e602d52d1513ccea0b07d8ea7d4d", [:mix], [], "hexpm"},