[Glitch] Fix light mode colors for advanced interface banner

Port cfd21eee96 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/styles/components/columns.scss

@@ -229,8 +229,8 @@ $ui-header-height: 55px;
 }
 
 .switch-to-advanced {
-  color: $classic-primary-color;
+  color: $light-text-color;
-  background-color: $classic-base-color;
+  background-color: $ui-base-color;
   padding: 15px;
   border-radius: 4px;
   margin-top: 4px;