Test new double toolchain install

Author: jonasbb

.github/workflows/ci.yaml

@@ -9,9 +9,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: actions-rust-lang/setup-rust-toolchain@v1
+      - uses: actions-rust-lang/setup-rust-toolchain@main
         with:
-          toolchain: nightly stable
+          toolchain: nightly,stable
           components: rustfmt,clippy
       - run: cargo +nightly --version
       - run: cargo +stable --version
+      - run: rustup override list