Upgrade rust/crates/async-trait to 0.1.38

Change-Id: I894c990c19b1ac3d74e4bf002cf581b9875e730e
diff --git a/METADATA b/METADATA
index 889b98f..ebd3009 100644
--- a/METADATA
+++ b/METADATA
@@ -9,11 +9,11 @@
     type: GIT
     value: "https://github.com/dtolnay/async-trait"
   }
-  version: "0.1.36"
+  version: "0.1.38"
   license_type: NOTICE
   last_upgrade_date {
     year: 2020
     month: 8
-    day: 11
+    day: 17
   }
 }