Fix container for aconfig flags.

This app is in system_ext, not system.

Bug: b/325307746
Test: manual
Flag: NA
Change-Id: Ibb1c7a4b338b6bf900a626e7ec66a28e0f90169d
diff --git a/aconfig/Android.bp b/aconfig/Android.bp
index 5413601..bca7494 100644
--- a/aconfig/Android.bp
+++ b/aconfig/Android.bp
@@ -20,7 +20,7 @@
 aconfig_declarations {
     name: "com_android_launcher3_flags",
     package: "com.android.launcher3",
-    container: "system",
+    container: "system_ext",
     srcs: ["**/*.aconfig"],
 }