Explicitly set generate_hashtree: false

Non-updatable APEXes are going to be only present on a dm-verity
protected read-only partition. For such APEXes there is no need in
embedding a hashtree.

This is a no-op change in preparation of switching default value of
generate_hashtree to true.

Bug: 190621617
Test: m
Change-Id: Ib9ceb38f316a06e4a39750adb94561c368b9d6f6
diff --git a/apex/Android.bp b/apex/Android.bp
index ec8a964..7daf1fe 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -48,6 +48,7 @@
         "i18n-bootclasspath-fragment",
     ],
     updatable: false,
+    generate_hashtree: false,
 }
 
 apex_key {