Upgrade rust/crates/async-trait to 0.1.40

Test: make
Change-Id: Ifae614e646fac929455de2cb4639578ae954a7f9
diff --git a/METADATA b/METADATA
index 4bc9e4e..059a608 100644
--- a/METADATA
+++ b/METADATA
@@ -7,13 +7,13 @@
   }
   url {
     type: ARCHIVE
-    value: "https://static.crates.io/crates/async-trait/async-trait-0.1.38.crate"
+    value: "https://static.crates.io/crates/async-trait/async-trait-0.1.40.crate"
   }
-  version: "0.1.38"
+  version: "0.1.40"
   license_type: NOTICE
   last_upgrade_date {
     year: 2020
-    month: 8
-    day: 17
+    month: 9
+    day: 1
   }
 }