move privapp_whitelist_com.android.storagemanager to system_ext

As StorageManager, permissions.xml should follow the app's partition.

Test: m && check booting
Bug: 137908189
Change-Id: Ie791b5fbe1b1906537a57e8f1c34029c0f092afc
diff --git a/data/etc/Android.bp b/data/etc/Android.bp
index 43f65e3..183c04e 100644
--- a/data/etc/Android.bp
+++ b/data/etc/Android.bp
@@ -120,7 +120,7 @@
 
 prebuilt_etc {
     name: "privapp_whitelist_com.android.storagemanager",
-    product_specific: true,
+    system_ext_specific: true,
     sub_dir: "permissions",
     src: "com.android.storagemanager.xml",
     filename_from_src: true,