chore: update the target compiler version to nightly-2021-12-01

yvt · yvt · commit 3248a53865db · 2021-12-03T12:57:44.000+09:00
diff --git a/rust-toolchain b/rust-toolchain
@@ -1 +1 @@
-nightly-2021-10-18
+nightly-2021-12-01
