Remove boilerplate.

The apex hash tree is automatically generated at compile time for
apexes in apexd-bootstrap, so there's no need to explicitly specify
anything here.

Bug: b/203820392, b/198361718
Test: presubmit
Change-Id: I5ff0363fde701e7fe4e3ed8ab274c6a57852828c
diff --git a/apex/Android.bp b/apex/Android.bp
index 4879f47..90a14b2 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -58,7 +58,6 @@
         "bionic-linker-config",
     ],
     updatable: false,
-    generate_hashtree: false,
 }
 
 sdk {