fix android exitPip invalid problem

Flutter/android/src/main/AndroidManifest.xml

@@ -12,7 +12,7 @@
                 android:excludeFromRecents="true"
                 android:exported="true"
                 android:resizeableActivity="true"
-                android:launchMode="singleTop"
+                android:launchMode="singleTask"
                 android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
                 android:hardwareAccelerated="true"
                 android:windowSoftInputMode="stateHidden"