build: bump rust-toolchain

Brooooooklyn · Brooooooklyn · commit f7c9a014faf8 · 2021-09-01T11:28:35.000+08:00
diff --git a/rust-toolchain b/rust-toolchain
@@ -1 +1 @@
-nightly-2021-07-06
+nightly-2021-08-17
