feat: scrollbar always visible if content scrolls on about

verified this shows the scrollbar only when the content actually
scrolls, so large phones won't see a useless scrollbar but now small
phones won't have a sometimes-invisible scrollbar exactly when a user
that needs help needs to know they can scroll down for debug info

AnkiDroid/src/main/res/layout/about_layout.xml

@@ -19,6 +19,7 @@
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
+    android:fadeScrollbars="false"
     android:layout_width="match_parent"
     android:layout_height="wrap_content">
 <LinearLayout