Update futures-executor to 0.3.21

Test: cd external/rust/crates && atest --host -c
Change-Id: I1efc86dbaa62d6b454dc46f879f7b7a82fe52d4f
diff --git a/METADATA b/METADATA
index 0a1c47b..26071bc 100644
--- a/METADATA
+++ b/METADATA
@@ -7,13 +7,13 @@
   }
   url {
     type: ARCHIVE
-    value: "https://static.crates.io/crates/futures-executor/futures-executor-0.3.17.crate"
+    value: "https://static.crates.io/crates/futures-executor/futures-executor-0.3.21.crate"
   }
-  version: "0.3.17"
+  version: "0.3.21"
   license_type: NOTICE
   last_upgrade_date {
-    year: 2021
-    month: 9
-    day: 22
+    year: 2022
+    month: 3
+    day: 1
   }
 }