Remove confirm exit option

Redundant with predictive back, but also just sort of pointless since it doesn't help
with any sort of app state retention.

core/src/main/java/tachiyomi/core/util/system/ImageUtil.kt

@@ -329,7 +329,7 @@ object ImageUtil {
                     "$partCount parts @ ${optimalSplitHeight}px height per part"
             }
 
-            return mutableListOf<SplitData>().apply {
+            return buildList {
                 val range = 0 until partCount
                 for (index in range) {
                     // Only continue if the list is empty or there is image remaining