Removed unwanted requires of and fixed rubocop errors

activerecord/test/cases/fixtures_test.rb

@@ -32,7 +32,6 @@ require "models/task"
 require "models/topic"
 require "models/traffic_light"
 require "models/treasure"
-require "tempfile"
 
 class FixturesTest < ActiveRecord::TestCase
   include ConnectionHelper

activesupport/test/ordered_options_test.rb

@@ -41,9 +41,9 @@ class OrderedOptionsTest < ActiveSupport::TestCase
 
     a[:test_key] = 56
     assert_equal 56, a.test_key
-    assert_equal 56, a['test_key']
+    assert_equal 56, a["test_key"]
     assert_equal 56, a.dig(:test_key)
-    assert_equal 56, a.dig('test_key')
+    assert_equal 56, a.dig("test_key")
   end
 
   def test_method_access

railties/test/commands/credentials_test.rb

@@ -5,7 +5,6 @@ require "env_helpers"
 require "rails/command"
 require "rails/commands/credentials/credentials_command"
 require "fileutils"
-require "tempfile"
 
 class Rails::Command::CredentialsCommandTest < ActiveSupport::TestCase
   include ActiveSupport::Testing::Isolation, EnvHelpers