Upgrade rust/crates/async-trait to 0.1.42

Test: make
Change-Id: I59704fdd852efc7dc64f6cf733093632653b0313
diff --git a/Android.bp b/Android.bp
index 4e87f35..c5fb16d 100644
--- a/Android.bp
+++ b/Android.bp
@@ -15,5 +15,5 @@
 // dependent_library ["feature_list"]
 //   proc-macro2-1.0.24 "default,proc-macro"
 //   quote-1.0.7 "default,proc-macro"
-//   syn-1.0.48 "clone-impls,default,derive,extra-traits,full,parsing,printing,proc-macro,quote,visit,visit-mut"
+//   syn-1.0.51 "clone-impls,default,derive,extra-traits,full,parsing,printing,proc-macro,quote,visit,visit-mut"
 //   unicode-xid-0.2.1 "default"