Update CI config

Author: taiki-e

.github/workflows/ci.yml

@@ -66,7 +66,7 @@ jobs:
       - uses: actions/checkout@v3
       - name: Install Rust
         run: rustup update stable
-      - run: cargo fmt --all -- --check
+      - run: cargo fmt --all --check
 
   miri:
     runs-on: ubuntu-latest

.github/workflows/release.yml

@@ -5,19 +5,12 @@ on:
     tags:
       - v[0-9]+.*
 
-env:
-  RUSTFLAGS: -D warnings
-  RUST_BACKTRACE: 1
-
 jobs:
   create-release:
     if: github.repository_owner == 'smol-rs'
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - name: Install Rust
-        run: rustup update stable
-      - run: cargo package
       - uses: taiki-e/create-gh-release-action@v1
         with:
           changelog: CHANGELOG.md