build(ci): explicitly use nightly toolchain

Author: OliverNChalk

.github/workflows/ci.yml

@@ -87,7 +87,7 @@ jobs:
           token: ${{ secrets.CI_READ }}
           toolchain: nightly
       - run: rustup component add rustfmt
-      - run: cargo fmt --all --check
+      - run: cargo +nightly fmt --all --check
 
   clippy:
     needs: skip-duplicates