build wheels with stable rust (#227)

* build wheels with stable rust

* [skip ci] revert if comment

Author: samuelcolvin

.github/workflows/ci.yml

@@ -308,6 +308,7 @@ jobs:
         with:
           command: sdist
           args: --out dist
+          rust-toolchain: stable
 
       - name: build wheels
         uses: messense/maturin-action@v1
@@ -316,6 +317,7 @@ jobs:
           manylinux: ${{ matrix.manylinux || 'auto' }}
           container: ${{ matrix.container }}
           args: --release --out dist --interpreter ${{ matrix.interpreter || '3.7 3.8 3.9 3.10 pypy3.7 pypy3.8 pypy3.9' }}
+          rust-toolchain: stable
 
       - run: ${{ matrix.ls || 'ls -lh' }} dist/