[Fontconfig] Make FontElement class non abstract

Author: ViliusSutkus89

pdf2htmlEX/src/main/java/com/viliussutkus89/android/pdf2htmlex/FontconfigAndroid.java

@@ -118,7 +118,7 @@ static void init(@NonNull AssetManager assetManager, @NonNull File cacheDir, @No
         }
     }
 
-    abstract static class FontElement {
+    static class FontElement {
         protected String alias;
         protected String family;