Revert "Merge branch 'refactor-avatars' into 'master'"

...ssets/javascripts/boards/components/board_list_header.vue

app/assets/javascripts/diffs/components/commit_item.vue

app/assets/javascripts/gfm_auto_complete.js

...ascripts/sidebar/components/assignees/assignee_avatar.vue

...ascripts/sidebar/components/reviewers/reviewer_avatar.vue

app/assets/javascripts/users_select/index.js

.../vue_merge_request_widget/components/mr_widget_author.vue

...ed/alert_details/components/sidebar/sidebar_assignees.vue

app/assets/stylesheets/components/avatar.scss

app/assets/stylesheets/framework/dropdowns.scss

app/assets/stylesheets/framework/lists.scss

...assets/stylesheets/page_bundles/_ide_theme_overrides.scss

app/assets/stylesheets/page_bundles/ide.scss

app/assets/stylesheets/page_bundles/projects.scss

app/assets/stylesheets/pages/groups.scss

app/assets/stylesheets/themes/dark_mode_overrides.scss

app/assets/stylesheets/vendors/atwho.scss

app/helpers/avatars_helper.rb

app/helpers/projects_helper.rb

app/helpers/sidebars_helper.rb