fix: credo issues and dialyxir warnings

lib/hcaptcha/http.ex

@@ -45,9 +45,8 @@ defmodule Hcaptcha.Http do
 
     result =
       with {:ok, response} <-
-             HTTPoison.post(url, body, @headers, timeout: timeout),
-           {:ok, data} <- @json_library.decode(response.body) do
-        {:ok, data}
+             HTTPoison.post(url, body, @headers, timeout: timeout) do
+        @json_library.decode(response.body)
       end
 
     case result do

mix.exs

@@ -58,7 +58,7 @@ defmodule Hcaptcha.Mixfile do
       {:jason, "~> 1.4", optional: true},
       {:credo, "~> 1.7.1", only: [:dev, :test], runtime: false},
       {:ex_doc, "0.30.6", only: :dev},
-      {:dialyxir, "~> 1.4.1", only: [:test]},
+      {:dialyxir, "~> 1.4.1", only: [:test], runtime: false},
       {:excoveralls, "~> 0.17.1", only: :test}
     ]
   end

test/hcaptcha_test.exs

@@ -2,7 +2,7 @@ defmodule HcaptchaTest do
   use ExUnit.Case, async: true
 
   # see https://docs.hcaptcha.com/#integration-testing-test-keys
-  @hCaptcha_test_secret "0x0000000000000000000000000000000000000000"
+  @hcaptcha_test_secret "0x0000000000000000000000000000000000000000"
 
   test "When the supplied hcaptcha-response is invalid, errors are returned" do
     assert {:error, messages} = Hcaptcha.verify("not_valid")
@@ -12,13 +12,13 @@ defmodule HcaptchaTest do
   test "When a valid response is supplied, a success response is returned" do
     assert {:ok, %{challenge_ts: _, hostname: _}} =
              Hcaptcha.verify("10000000-aaaa-bbbb-cccc-000000000001",
-               secret: @hCaptcha_test_secret
+               secret: @hcaptcha_test_secret
              )
   end
 
   test "When an invalid response is supplied, an error response is returned" do
     assert {:error, [:invalid_input_response]} =
-             Hcaptcha.verify("invalid_response", secret: @hCaptcha_test_secret)
+             Hcaptcha.verify("invalid_response", secret: @hcaptcha_test_secret)
   end
 
   test "When secret is not overridden the configured secret is used" do