Upgrade rust/crates/protobuf-codegen to 2.16.2

Test: make
Change-Id: I14166e5bd65e98c7c7a53cff992df72164346bc5
diff --git a/README.android b/README.android
index 93d2ac7..a75eb35 100644
--- a/README.android
+++ b/README.android
@@ -8,7 +8,7 @@
 
         // Hack: hard code version number here because Android.bp
         // rust modules cannot pass it though env variable yet.
-        w.write_generated_by("rust-protobuf", "2.14.0");
+        w.write_generated_by("rust-protobuf", "2.16.2");
 
 If there are non-trivial changes in build.rs or src/lib.rs,
 please rerun cargo2android.py and verify the differences in