Set the container field of aconfig flags

Test: m
Bug: 312769710
Change-Id: I1eed7982b40d28947aa3f9575c568eac325dc832
diff --git a/common/FlaggedApi.bp b/common/FlaggedApi.bp
index 2cb9b2f..c382e76 100644
--- a/common/FlaggedApi.bp
+++ b/common/FlaggedApi.bp
@@ -17,6 +17,7 @@
 aconfig_declarations {
     name: "com.android.net.flags-aconfig",
     package: "com.android.net.flags",
+    container: "system",
     srcs: ["flags.aconfig"],
     visibility: ["//packages/modules/Connectivity:__subpackages__"],
 }