Enable ballooning in aarch64

Bug: 392795840
Test: check if terminal app work well even with large memory usage
Change-Id: Iefaf20cdd27a21db5eed0b0736a25d8766bda819
diff --git a/build/debian/vm_config.json.aarch64 b/build/debian/vm_config.json.aarch64
index d41a29c..96254f8 100644
--- a/build/debian/vm_config.json.aarch64
+++ b/build/debian/vm_config.json.aarch64
@@ -34,5 +34,6 @@
     "debuggable": true,
     "console_out": true,
     "console_input_device": "ttyS0",
-    "network": true
+    "network": true,
+    "auto_memory_balloon": true
 }