Remove unused variables (#3906)

.eslintrc.yml

app/javascript/mastodon/actions/accounts.js

app/javascript/mastodon/actions/domain_blocks.js

app/javascript/mastodon/actions/notifications.js

app/javascript/mastodon/actions/statuses.js

app/javascript/mastodon/components/dropdown_menu.js

app/javascript/mastodon/components/media_gallery.js

app/javascript/mastodon/components/status.js

app/javascript/mastodon/components/status_content.js

app/javascript/mastodon/components/status_list.js

app/javascript/mastodon/containers/mastodon.js

app/javascript/mastodon/containers/status_container.js

...javascript/mastodon/features/account/components/header.js

app/javascript/mastodon/features/account_gallery/index.js

...features/community_timeline/components/column_settings.js

...ommunity_timeline/containers/column_settings_container.js

app/javascript/mastodon/features/community_timeline/index.js

...ript/mastodon/features/compose/components/compose_form.js

...odon/features/compose/components/emoji_picker_dropdown.js

...pt/mastodon/features/compose/components/navigation_bar.js