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/flavours/glitch/styles/components/local_settings.scss

@@ -125,7 +125,7 @@
   margin-bottom: 10px;
 }
 
-@media screen and (max-width: 630px) {
+@media screen and (width <= 630px) {
   .glitch.local-settings__navigation {
     width: 40px;
     flex-shrink: 0;