Update Rust toolchain version

Change-Id: Idb35a05955d4e7feb241717895bc988a1035e5aa
diff --git a/fuchsia.ensure b/fuchsia.ensure
index 2489e74..c0115a1 100644
--- a/fuchsia.ensure
+++ b/fuchsia.ensure
@@ -34,7 +34,7 @@
 
 # Rust
 @Subdir rust
-fuchsia/rust/${platform} git_revision:71340ca4e181b824bcefa887f1be60dd0b7352ce
+fuchsia/rust/${platform} git_revision:8a28d94ea1b6c19b7e1d41ef9b33ccb73951f654
 
 # Swift
 @Subdir swift