Merge branch 'remove-jquery-ui-sortable' into 'master'

app/assets/javascripts/application.js

app/assets/javascripts/boards/boards_bundle.js.es6

app/assets/javascripts/label_manager.js.es6

app/assets/javascripts/milestone.js

app/assets/javascripts/test_utils/simulate_drag.js

app/assets/stylesheets/framework/jquery.scss

app/assets/stylesheets/pages/labels.scss

app/assets/stylesheets/pages/milestone.scss

app/views/groups/milestones/show.html.haml

app/views/projects/boards/_show.html.haml

app/views/projects/labels/index.html.haml

app/views/projects/milestones/show.html.haml

app/views/shared/milestones/_issuable.html.haml

changelogs/unreleased/remove-jquery-ui-sortable.yml

config/webpack.config.js

spec/features/boards/boards_spec.rb

spec/features/milestones/milestones_spec.rb

spec/features/projects/labels/update_prioritization_spec.rb

spec/support/drag_to_helper.rb