Updated rules_rust to version `0.8.1`. (#1484)

diff --git a/version.bzl b/version.bzl
index 2690d69..15b9068 100644
--- a/version.bzl
+++ b/version.bzl
@@ -1,3 +1,3 @@
 """The version of rules_rust."""
 
-VERSION = "0.8.0"
+VERSION = "0.8.1"