优化：移除multidex

注：Android 5.0（api21）开始，默认支持multidex，不需要手动接入multidex

app/src/main/java/io/legado/app/App.kt

@@ -1,12 +1,12 @@
 package io.legado.app
 
+import android.app.Application
 import android.app.NotificationChannel
 import android.app.NotificationManager
 import android.content.Context
 import android.content.pm.ActivityInfo
 import android.content.res.Configuration
 import android.os.Build
-import androidx.multidex.MultiDexApplication
 import com.github.liuyueyi.quick.transfer.ChineseUtils
 import com.github.liuyueyi.quick.transfer.constants.TransType
 import com.jeremyliao.liveeventbus.LiveEventBus
@@ -33,7 +33,7 @@ import splitties.init.appCtx
 import splitties.systemservices.notificationManager
 import java.util.concurrent.TimeUnit
 
-class App : MultiDexApplication() {
+class App : Application() {
 
     private lateinit var oldConfig: Configuration