Fix sass-lint config (#10982)

.sass-lint.yml

app/javascript/styles/contrast/diff.scss

app/javascript/styles/contrast/variables.scss

app/javascript/styles/mailer.scss

app/javascript/styles/mastodon/_mixins.scss

app/javascript/styles/mastodon/admin.scss

app/javascript/styles/mastodon/basics.scss

app/javascript/styles/mastodon/components.scss

app/javascript/styles/mastodon/containers.scss

app/javascript/styles/mastodon/emoji_picker.scss

app/javascript/styles/mastodon/forms.scss

app/javascript/styles/mastodon/polls.scss

app/javascript/styles/mastodon/rtl.scss

package.json