DEV: update deprecated icon name from caret-square-down to square-caret-down

Author: tyb-talks

about.json

@@ -7,7 +7,7 @@
   "assets": {},
   "modifiers": {
     "svg_icons": [
-      "caret-square-down"
+      "square-caret-down"
     ]
   }
 }

javascripts/discourse/components/custom-header-links.gjs

@@ -40,7 +40,7 @@ export default class CustomHeaderLinks extends Component {
       {{#if this.site.mobileView}}
         <span class="btn-custom-header-dropdown-mobile">
           <DButton
-            @icon="caret-square-down"
+            @icon="square-caret-down"
             @title={{i18n "custom_header.discord"}}
             @action={{this.toggleHeaderLinks}}
           />