Hardcode toolchain version to stable

Author: alexdewar

.github/workflows/cargo-build-and-test.yml

@@ -17,13 +17,11 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
-        toolchain:
-          - stable
     steps:
       - uses: actions/checkout@v4
       - uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-          toolchain: ${{ matrix.toolchain }}
+          toolchain: stable
       - run: cargo test --verbose
 
       - if: ${{ matrix.os == 'ubuntu-latest' }}