Remove some minor settings

Some spring cleaning to remove some unnecessary complexity so things are easier to maintain.

- Start screen: redundant with app shortcuts in Android 7.1+
- Jump to chapters: irrelevant in tablet mode and people can scroll a tiny bit if they really have to
- Option to not scroll away bottom nav: issues with fast scroll will be irrelevant with it being replaced or removed in the Compose migrations

Get ready for people malding over their special needs. https://xkcd.com/1172/

app/src/main/res/layout/main_activity.xml

@@ -86,6 +86,7 @@
         android:layout_height="wrap_content"
         android:layout_gravity="bottom"
         android:clickable="true"
+        app:layout_behavior="eu.kanade.tachiyomi.widget.HideBottomNavigationOnScrollBehavior"
         app:layout_insetEdge="bottom"
         app:menu="@menu/main_nav"
         tools:ignore="KeyboardInaccessibleWidget" />