chore: 🤖 Update DC main element padding (#2009)

Update Desktop Client main element padding to look like app-frame HDS implementation within cloud-ui.

✅ Closes: https://hashicorp.atlassian.net/browse/ICU-10497

ui/desktop/app/styles/app.scss

@@ -37,6 +37,11 @@
     overflow: auto;
 
     main {
+      /** This overrides the main defined within Rose.
+       * HDS has this set to 1.5rem top/bottom 3rem left/right. HDS assumes the usage of breadcrumbs
+       * but the DC have no breadcrumbs, so we will keep it at 3rem all around.
+      */
+      padding: 3rem;
       flex-grow: 1;
     }
   }