Remove magic comments from Ruby files

Since Ruby 2, UTF-8 is the default encoding, which make many magic
comments omissible.
https://www.ruby-lang.org/en/news/2013/02/24/ruby-2-0-0-p0-is-released/

Related to: https://gitlab.com/gitlab-org/gitlab-foss/merge_requests/5456

.rubocop_todo.yml

@@ -565,11 +565,6 @@ Style/EmptyLiteral:
 Style/EmptyMethod:
   Enabled: false
 
-# Offense count: 40
-# Cop supports --auto-correct.
-Style/Encoding:
-  Enabled: false
-
 # Offense count: 203
 # Cop supports --auto-correct.
 # Configuration parameters: EnforcedStyle.

app/helpers/page_layout_helper.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 module PageLayoutHelper

app/models/commit.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 class Commit

ee/spec/controllers/projects/jobs_controller_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

ee/spec/lib/container_registry/client_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

ee/spec/lib/gitlab/elastic/search_results_spec.rb

-# coding: utf-8
 require 'spec_helper'
 
 describe Gitlab::Elastic::SearchResults, :elastic do

ee/spec/lib/gitlab/regex_spec.rb

-# coding: utf-8
 require 'spec_helper'
 
 describe Gitlab::Regex do

ee/spec/requests/api/project_mirror_spec.rb

-# -*- coding: utf-8 -*-
 require 'spec_helper'
 
 describe API::ProjectMirror do

ee/spec/workers/post_receive_spec.rb

-# coding: utf-8
 require 'spec_helper'
 
 describe PostReceive do

lib/api/helpers/services_helpers.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 module API

lib/gitlab/auth/ldap/dn.rb

-# -*- ruby encoding: utf-8 -*-
 # frozen_string_literal: true
 
 # Based on the `ruby-net-ldap` gem's `Net::LDAP::DN`

lib/gitlab/ee_compat_check.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 # rubocop: disable Rails/Output

lib/gitlab/profiler.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 module Gitlab

lib/gitlab/quick_actions/issuable_actions.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 module Gitlab

lib/gitlab/slash_commands/presenters/issue_move.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 module Gitlab

spec/controllers/application_controller_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 require 'spec_helper'
 

spec/controllers/concerns/send_file_upload_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

spec/controllers/projects/jobs_controller_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 require 'spec_helper'
 

spec/helpers/application_helper_spec.rb

-# coding: utf-8
 require 'spec_helper'
 
 describe ApplicationHelper do

spec/helpers/defer_script_tag_helper_spec.rb

-# coding: utf-8
 require 'spec_helper'
 
 describe DeferScriptTagHelper do

spec/lib/container_registry/client_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

spec/lib/gitlab/encoding_helper_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require "spec_helper"

spec/lib/gitlab/git/blame_spec.rb

-# coding: utf-8
 require "spec_helper"
 
 describe Gitlab::Git::Blame, :seed_helper do

spec/lib/gitlab/git/blob_spec.rb

-# encoding: utf-8
-
 require "spec_helper"
 
 describe Gitlab::Git::Blob, :seed_helper do

spec/lib/gitlab/git/conflict/file_spec.rb

-# coding: utf-8
 require 'spec_helper'
 
 describe Gitlab::Git::Conflict::File do

spec/lib/gitlab/git/repository_spec.rb

-# coding: utf-8
 require "spec_helper"
 
 describe Gitlab::Git::Repository, :seed_helper do

spec/lib/gitlab/git_spec.rb

-# coding: utf-8
 require 'spec_helper'
 
 describe Gitlab::Git do

spec/lib/gitlab/json_logger_spec.rb

-# coding: utf-8
 require 'spec_helper'
 
 describe Gitlab::JsonLogger do

spec/lib/gitlab/path_regex_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

spec/lib/gitlab/project_search_results_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

spec/lib/gitlab/regex_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

spec/lib/gitlab/search/found_blob_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

spec/lib/gitlab/url_blocker_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

spec/models/blob_spec.rb

-# encoding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'

spec/requests/api/projects_spec.rb

-# -*- coding: utf-8 -*-
 require 'spec_helper'
 
 shared_examples 'languages and percentages JSON response' do

spec/services/issues/update_service_spec.rb

-# coding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'