ohos: Add fallback font for serif (#32555)

The fallback behavior seems to have changed recently.
Now we need to explicitly add a fallback for `serif`
otherwise no font is selected.

Signed-off-by: Jonathan Schwender <jonathan.schwender@huawei.com>

components/fonts/platform/freetype/ohos/font_list.rs

@@ -80,6 +80,8 @@ impl FontList {
         let alternatives = [
             ("HarmonyOS Sans", "HarmonyOS_Sans_SC_Regular.ttf"),
             ("sans-serif", "HarmonyOS_Sans_SC_Regular.ttf"),
+            // Todo: It's unclear what font should be used, but we need to use something
+            ("serif", "HarmonyOS_Sans_SC_Regular.ttf"),
         ];
 
         alternatives