Fix SCSS linting issues (#2207)

* Disable font-family-no-missing-generic-family-keyword for font-awesome accessibility icons

* Run stylelint --fix

* Avoid `@extend` directives with doodle modal CSS

* Drop use of `@extend` for notification cleanup buttons SCSS

* Run prettier on SCSS

app/javascript/styles/mastodon/forms.scss

@@ -722,7 +722,7 @@ code {
     }
   }
 
-  @media screen and (max-width: 740px) and (min-width: 441px) {
+  @media screen and (width <= 740px) and (width >= 441px) {
     margin-top: 40px;
   }