set aconfig_declarations containers to system

Bug: 330354107
Test: CI

Flag: NONE

Ignore-AOSP-First: It is easier to detect all the mismatch in internal
master.

Change-Id: Ic1af43cf291fce8845011f083cef21a67bc6aab9
diff --git a/packages/SystemUI/aconfig/systemui.aconfig b/packages/SystemUI/aconfig/systemui.aconfig
index 4bfc629..112d964 100644
--- a/packages/SystemUI/aconfig/systemui.aconfig
+++ b/packages/SystemUI/aconfig/systemui.aconfig
@@ -1,4 +1,5 @@
 package: "com.android.systemui"
+container: "system"
 
 flag {
     name: "example_flag"