Build a nightly release of rustc-perf in CI

Author: Kobzol

.github/workflows/nightly.yml

@@ -22,7 +22,7 @@ jobs:
         uses: actions-rs/toolchain@v1
         with:
           profile: minimal
-          toolchain: 1.66.0
+          toolchain: stable
           override: true
 
       - uses: Swatinem/rust-cache@v1