Set the container field of aconfig flags

Test: m
Bug: 312769710
Change-Id: I63e922ffcfc96a27e6166252563b3633a5bc0b1a
diff --git a/bluetooth/audio/flags/btaudiohal.aconfig b/bluetooth/audio/flags/btaudiohal.aconfig
index 763777e..4c1500a 100644
--- a/bluetooth/audio/flags/btaudiohal.aconfig
+++ b/bluetooth/audio/flags/btaudiohal.aconfig
@@ -1,4 +1,5 @@
 package: "com.android.btaudio.hal.flags"
+container: "system"
 
 flag {
     name: "dsa_lea"