Use nightly fmt (#3254)

* fmt

* a

Author: tokatoka

.github/workflows/build_and_test.yml

@@ -216,7 +216,9 @@ jobs:
       MAIN_LLVM_VERSION: 20
     steps:
       - uses: actions/checkout@v4
-      - uses: ./.github/workflows/ubuntu-prepare
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt
       - uses: Swatinem/rust-cache@v2
         with: { shared-key: "ubuntu" }
       - name: Installing black