Use protobuf 2.x instead of 3.x

Ignore-AOSP-First: This will go into AOSP, but needs to be submitted
here because the topic includes internal changes.
Bug: 270895633
Test: build

Change-Id: I3a2fcd73b6d34c4314cc81de25601d9b67e73f70
diff --git a/microdroid/payload/metadata/Android.bp b/microdroid/payload/metadata/Android.bp
index cd182fc..e3138e8 100644
--- a/microdroid/payload/metadata/Android.bp
+++ b/microdroid/payload/metadata/Android.bp
@@ -12,7 +12,7 @@
     rustlibs: [
         "libanyhow",
         "libmicrodroid_metadata_proto_rust",
-        "libprotobuf",
+        "libprotobuf_deprecated",
     ],
     apex_available: [
         "com.android.virt",