Mix dependencies needs updating

[dagumak]

This is the error I received after running mix deps.get

Failed to use "phoenix_html" (version 3.1.0) because
  phoenix_ecto (version 4.4.0) requires ~> 2.14.2 or ~> 3.0
  phoenix_live_view (version 0.16.4) requires ~> 3.0
  phoenix_oauth2_provider (version 0.5.1) requires ~> 2.0
  pow (version 1.0.26) requires >= 2.0.0 and < 4.0.0
  mix.lock specifies 3.1.0

** (Mix) Hex dependency resolution failed, change the version requirements of your dependencies or unlock them (by using mix deps.update or mix deps.unlock). If you are unable to resolve the conflicts you can try overriding with {:dependency, "~> 1.0", override: true}

[fastjames]

I have opened danschultzer/ex_oauth2_provider#96 as the first step in updating these dependencies.

[filipecabaco]

Made a PR that helps bump the dependencies without the need to update ex_oauth_provider for now #46