Move reader preloading to IO scope

Maybe fixes #8440

(cherry picked from commit e052bdef96)

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -871,7 +871,7 @@ class ReaderActivity : BaseActivity() {
      * the viewer is reaching the beginning or end of a chapter or the transition page is active.
      */
     fun requestPreloadChapter(chapter: ReaderChapter) {
-        lifecycleScope.launch { viewModel.preloadChapter(chapter) }
+        lifecycleScope.launchIO { viewModel.preloadChapter(chapter) }
     }
 
     /**

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderViewModel.kt

@@ -388,21 +388,18 @@ class ReaderViewModel(
             return
         }
 
-        logcat { "Preloading ${chapter.chapter.url}" }
-
         val loader = loader ?: return
-        withIOContext {
         try {
+            logcat { "Preloading ${chapter.chapter.url}" }
             loader.loadChapter(chapter)
         } catch (e: Throwable) {
             if (e is CancellationException) {
                 throw e
             }
-                return@withIOContext
+            return
         }
         eventChannel.trySend(Event.ReloadViewerChapters)
     }
-    }
 
     /**
      * Called every time a page changes on the reader. Used to mark the flag of chapters being