Feat: Update apps/theming/css/default.css

Co-authored-by: Grigorii K. Shartsev <me@shgk.me>
Signed-off-by: Marco <marcoambrosini@proton.me>

apps/theming/css/default.css

@@ -49,10 +49,11 @@
   --default-font-size: 15px;
   --animation-quick: 100ms;
   --animation-slow: 300ms;
-  --border-radius-element: 10px; /** Nextcloud 29+ | temp variable to use old design */
   --border-radius: 3px;
   --border-radius-large: 10px;
   --border-radius-rounded: 28px;
+  /* Border radius of interactive elements such as buttons, input, navigation and list items. Available since Nextcloud 30. */
+  --border-radius-element: 10px; 
   --border-radius-pill: 100px;
   --default-clickable-area: 44px;
   --default-line-height: 24px;