Change font from Liberation Sans to Poppins

Liberation Sans is not loaded by rml_setup2.lua, but Poppins is.
This fixes the 'No font face defined' warning on select elements.

Author: claude

scen_edit/view/rcss/springboard.rcss

@@ -1,5 +1,5 @@
 body#springboard {
-    font-family: Liberation Sans;
+    font-family: Poppins;
     font-size: 14dp;
     color: #cccccc;
     width: 100%;