Start cleanup of "threads" page

app/serializers/merge_request_widget_entity.rb

...jects/_merge_request_merge_suggestions_settings.html.haml

app/views/projects/merge_requests/_widget.html.haml

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

doc/development/code_review.md

doc/user/admin_area/diff_limits.md

doc/user/discussions/index.md

doc/user/project/merge_requests/creating_merge_requests.md

doc/user/project/merge_requests/getting_started.md

doc/user/project/merge_requests/index.md

...t/merge_requests/reviewing_and_managing_merge_requests.md

...sts/reviews/img/add_another_suggestion_to_batch_v13_1.jpg

...uests/reviews/img/add_first_suggestion_to_batch_v13_1.jpg

...requests/reviews/img/apply_batch_of_suggestions_v13_1.jpg

...ect/merge_requests/reviews/img/apply_suggestion_v13_9.png

..._requests/reviews/img/comment-on-any-diff-line_v13_10.png

.../project/merge_requests/reviews/img/commit_nav_v13_11.png

...roject/merge_requests/reviews/img/custom_commit_v13_9.png

...project/merge_requests/reviews/img/file_by_file_v13_2.png

...e_requests/reviews/img/group_merge_requests_list_view.png