Remove legacy git_adapter helper method

test/test_app_helpers.rb

@@ -4,15 +4,6 @@ require File.expand_path(File.join(File.dirname(__FILE__), "helper"))
 context "Precious::Helpers" do
   include Precious::Helpers
 
-  test "return git adapter" do
-    if defined?(Gollum::GIT_ADAPTER)
-      result = Gollum::GIT_ADAPTER
-    else
-      Gollum::GIT_ADAPTER = result = 'grit'
-    end
-    assert_equal result, git_adapter
-  end
-
   test "extracting paths from URLs" do
     assert_nil extract_path('Eye-Of-Sauron')
     assert_equal 'Mordor', extract_path('Mordor/Sauron')