[rust] Roll Rust toolchain

Change-Id: If8ad30668a50e4eefc5b179a12e55719bc7b0681
diff --git a/fuchsia.ensure b/fuchsia.ensure
index 2a38551..a905b8a 100644
--- a/fuchsia.ensure
+++ b/fuchsia.ensure
@@ -45,7 +45,7 @@
 
 # Rust
 @Subdir rust
-fuchsia/rust/${platform} git_revision:8acec1f9d0b40dde142e6c26d7358b9ab232d2b4
+fuchsia/rust/${platform} git_revision:7c98d2e63f732682b057c8c453b08f9e12b262e6
 
 # Swift
 @Subdir swift