ci: use new cargo fmt option

Author: calebcartwright

.github/workflows/main.yml

@@ -23,4 +23,4 @@ jobs:
     - uses: actions/checkout@master
     - name: Install Rust
       run: rustup update stable && rustup default stable && rustup component add rustfmt
-    - run: cargo fmt -- --check
+    - run: cargo fmt --check