Doc CI to use stable rust

Author: cijothomas

.github/workflows/ci.yml

@@ -132,7 +132,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@nightly
+      - uses: dtolnay/rust-toolchain@stable
         with:
           components: rustfmt
       - uses: arduino/setup-protoc@v3