feat(flutter): 移除原生静态开屏

android/app/src/main/res/drawable-v21/launch_background.xml

@@ -3,9 +3,4 @@
 
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
     <item android:drawable="@color/splash_background" />
-    <item>
-        <bitmap
-            android:gravity="center"
-            android:src="@drawable/splash_icon" />
-    </item>
 </layer-list>