[rake] remove invalid/duplicative rspec option

rakelib/spec.rake

@@ -3,7 +3,7 @@ require 'rspec/core/rake_task'
 namespace :spec do
   desc 'Run all tests'
   RSpec::Core::RakeTask.new(:all) do |task|
-    task.rspec_opts = %w[--color --format documentation --order default]
+    task.rspec_opts = %w[--color --format documentation]
     task.pattern = 'spec/**/*_spec.rb'
   end
 end