Replace system_ext container with system

Bug: b/365135457
Test: m
Flag: EXEMPT refactor
Change-Id: I5521307c4b816d9802cb5f676d11c0b89cdfa862
diff --git a/aconfig/Android.bp b/aconfig/Android.bp
index bca7494..5413601 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_ext",
+    container: "system",
     srcs: ["**/*.aconfig"],
 }